From the artificier writeup:

Infusing an Item

Whenever you finish a long rest, you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item.

Do you have to wake up and immediately infuse everything you can or can you hold the infusion to some later time in the day?

For instance, the group is in a city and has two options, go speak with someone in charge as part of an investigation or head to the sewers? Option 1 means you’ll want the Perfume of Bewitching while option 2 means pulling out the goggles of night. (assuming both are known infusions). But, either way you don’t know the choice is even there till later in the game day. Can you hold 1 infusion and not declare it when you wake from a long rest?

Quote from Stormknight >>

In short, no, you can't. 🙂

You decide upon the infusions and they happen at the point that the long rest completes.

 Anything office on that or just your reading?

The rules for infusing items explicitly state "When you finish a long rest..." You can't delay regaining class features or spell slots which are also granted when you finish a long rest, so I'd say it's pretty explicit from the rules as written. If it were intended to be done later, it would could be worded "anytime after" but the word "when" does imply immediate causation. Additionally, you don't sleep for the full eight hours of a long rest in 5e (I think typically the understanding is it's about six hours of sleep and then two hours of prep, gear maintenance, and other busy work, but I haven't read that section recently) so if your objection is that it's weird to just spring awake and infuse something then technically that's not required in 5e.

I think mechanically infusions as part of a long rest make sense because that reflects the time an Artificer spends tinkering and modifying and otherwise manipulating items. There's no indication that you can infuse as an action of any type, so it pretty clearly takes effect as part of a rest (such as regaining spell slots for casters, excluding a few class features). By lacking an action designation, I don't think there's a reasonable way to say that it's quick enough to work immediately without prep or a workspace. If you really wanted to fight on this, I suppose I could see the argument of doing an infusion during a short rest, since a long rest lets you make all your possible infusions (at least two) and you have two hours of flexible time, while a short rest is one hour, but I think you'd be hard pressed to justify any faster usage of the ability.

(EDIT: Yep there is see botom addition)
Is there a notation about long rests being only once per 24 hours?  I don't remember off hand but I think I heard someone mention it once. 
if not, if you were an Elf-or dipped the Returned Rogue (which a 3lv dip is tempting because you can switch tool profiency daily which pairs well with right tool feature. Also nets you a bonus action for movements or a necrotic damage (sadly does not work witn your alchemist lv 5 skill tho) equal to your sneak attack+dex.) 

Either one of those would let you spend 4 hours for a long rest, which could potentially let you switch things out if plans change rapidly. (and as an alchemist potentially ehlp your potion/spell slot situation)

Edit: A character can't benefit from more than one long rest in a 24-hour period, and a character must have at least 1 hit point at the start of the rest to gain its benefits.
Though, I wonder if being allowed to change things is the benefit its talking about- or if the benefit is only referring to the HP/resource restoration.
Probably all of it

Quote from SquireZed >>

The rules for infusing items explicitly state "When you finish a long rest..." You can't delay regaining class features or spell slots which are also granted when you finish a long rest, so I'd say it's pretty explicit from the rules as written. If it were intended to be done later, it would could be worded "anytime after" but the word "when" does imply immediate causation. 

 I was hoping it was a bit more like wizard in that a wizard regains spell slots but doesn't have to pick all their spells immediately. It would add a bit more versatility to artificier and allow more than just a combat build in most cases.

In general, I gotta say Artificer needs to up the versalitiy.   if I were to make one alteration to the class in general, it would be to give them more versatility in terms of when and what they're doing.  bring back the switch cantrips daily. Let you switch infusions 1/day rather than specifically at morning. something like that.

The first link is too generic and applies to clerics, druids, paladins, or other classes that get their spells once per day.

From the PHB: "You can change your list of prepared spells when you finish a long rest. Preparing a new list of wizard spells requires time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell: at least 1 minute per spell level for each spell on your list."

Otherwise there is no reason to put in the time required to change a wizard's spell list per spell level.

Edit: hit post too early.

Which isn't really the point of my question. I was wondering if there is anything official for artificiers and infusions. Unless you know there won't be combat or some other important issue is occurring, it basically means the artificier is limited to a combat-centric build out. I realize that there will be people that have to have that not-directly related to combat item like an alchemy jug or bag of holding.

I usually solve this by having the post long rest meal/prep time thing the time when I ask the group for the plan today.  And adjust according to the plan.

Sure things will change during th day, sometimes drastically.. But thats the best ya can do.  Its not much different than any prepared caster chosing spells for the original plan and coming up short when stuff occurs.  (but I also always have alchemy jug-because I am stock piling Acid and Oil to use).

It would be neat if you could switch 1 infusion on a short rest or something. or 1/day. or if there was a spell (like level 1) that would let you switch it.  I'd spend a spell slot to alter an infusion. Personally I"m hoping they add Artificer specific unique spells in the future.  This being one of them. The other being spells for mas sproducing Alchemical Weapons for cheaper and faster- A bit like that holy water spell maybe.  But more production. 
Also hoping for unique infusions for non combat stuff. Such as an Infusion choice that helps you produce Consumables cheaper.  

I think those are all design spaces that would be real fun and fit the class

Quote from Discfan2 >>

The first link is too generic and applies to clerics, druids, paladins, or other classes that get their spells once per day.

 "You prepare the list of cleric (wizard) spells that are available for you to cast, choosing from the cleric (wizard) spell list. When you do so, choose a number of cleric spells (wizard spells from your spellbook) equal to your Wisdom (Intelligence) modifier + your cleric (wizard) level (minimum of one spell). The spells must be of a level for which you have spell slots.

For example, if you are a 3rd-level cleric (wizard), you have four 1st-level and two 2nd-level spell slots. With a Wisdom (Intelligence) of 16, your list of prepared spells can include six spells of 1st or 2nd level, in any combination. If you prepare the 1st-level spell cure wounds (magic missile), you can cast it using a 1st-level or 2nd-level slot. Casting the spell doesn’t remove it from your list of prepared spells.

You can change your list of prepared spells when you finish a long rest. Preparing a new list of cleric (wizard) spells requires time spent in prayer and meditation (time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell): at least 1 minute per spell level for each spell on your list."

Wizards prepare and cast spells the same way that clerics and druids do; the linked section of the Sage Advice Compendium absolutely applies to wizards.

 The one minute per spell level is a limiter on what the wizard can dump and prepare. "When you finish a long rest," means the spells are replaced at the point the eight hours finishes. This means during your long rest, you've been preparing. A long rest is defined as six hours sleep and two hours light activity. So you have two hours to prepare spells. Going by spell slots alone, if you dump everything and prepare all new, that is 90 minutes of your 120. This doesn't leave you much time for anything else. 95% of the time, it won't come up, but it is there for DMs to have something to complicate things for a wizard in the party.

You either get a long rest or you don't. There is no complication outside of some corner case homebrews.