We generally don't use short rests too much so something we are talking about doing at my table is allowing warlocks and by extension monks, to regain spell slots after 15 minutes of not using spell slots or combat the number of times equals to the characters proficiency bonus times per day. What do you guys think? is that too many times a day to reset their spell slots or does that sound about right? 

The game is built around the assumption that in your average demanding adventuring day you'll have one long rest, and two or three short rests, so I think proficiency bonus will definitely be too many.

What I would say is, before homebrewing a change the obvious question is; why don't you take short rests? When I'm playing a short rest bound character I will push for short rests when I need them, and make clear to others what the consequences are if we don't take one, i.e- as a Monk I may not help in the front lines anymore, or as a warlock we'll have no access to spells that only I have, as a Fighter I won't have Action Surge or Second Wind etc.

As long as the party is clear that the trade off is an hour of game time for a more effective party member then it's a decision to be made. Basically I try to push selfish long-rest bound players into thinking in terms of the benefit to the party, because that's also a benefit to themselves; for example, a Sorcerer may not have any short rest resources, but if the party's Monk can no longer run interference effectively then suddenly the Sorcerer is more vulnerable to enemy attack, so short resting is actually a benefit to them as well.

The real question behind this though is, what is the actual cost of a short rest in your campaign? If you don't worry too much about timings then a game hour spent resting is inconsequential, but if the campaign heavily features timed events where an hour wasted could mean the difference between saving a village or finding it already slaughtered, or you're often in environments where you can't rest, then you're going to feel punished every time you need to. If the campaign is more the latter then players and the DM need to discuss where the balance is, because punishing short rest bound players for the classes they've picked isn't fun, but short rests also shouldn't be seen as free of charge either as timing should matter.

You might discuss things like having only some of the group rest, e.g- those who don't need to rest can scout ahead at a comfortable pace, until those who rested are able to catch up with a forced march or something. Alternatively you might simply reduce the time required for a short rest to half an hour, or 15 minutes or whatever, you just need to find the right balancing point.

We don’t usually use short rests simply out of a lack of need, situation and pacing. We don’t usually have characters that are dependent on short rests, we use hit dice to recover hit points on a long rest and we integrate an “extended rest” for complete healing. So with the exception of maybe a wizards arcane recovery short rests just aren’t a thing for us. 

It sounds like you're using the gritty realism optional rules for HP but not for other kinds of resources. Consider introducing this rule in its fullest. 

Alternatively, what Haravikk said is very true. Make everyone understand that if one party member is weakened, everyone are. I remember once when my party got mad at the Fighter for taking a short rest when he had low HP and no resources, so they left him alone and went into a haunted fortress. Of course, it ended up with one of them dead and the others on the brink of death. They still think the Fighter is to blame, but that's a different matter.

I don't think your optional rule is necessarily bad before level 9, but it's not without problems. Depending on the type of campaign, this can either be rarely used or used to its fullest every day. The former is the more problematic, and a game where you never take short rests is one I assume will have little time without combat, either.

One more thing to consider is to remind your party that people (even the fantasy races,I'm sure) need to eat, drink and rest from time to time. Maybe just take short rests for the sake of realism? It can be a great opportunity to roleplay among the players.

Quote from Jessebruffett >>

We don’t usually use short rests simply out of a lack of need, situation and pacing. We don’t usually have characters that are dependent on short rests, we use hit dice to recover hit points on a long rest and we integrate an “extended rest” for complete healing. So with the exception of maybe a wizards arcane recovery short rests just aren’t a thing for us. 

 I mean different parties have different needs. If you have a monk or warlock or fighter in the party, you can no longer say you don't do it out of "lack of need" unless you mean the players behind those characters are too shy to ask for it (although it sounds like the wizard is a bit more assertive?).

At any rate, ki and pact slots already scale with level, and double scaling by proficiency bonus is going to get out of hand in later levels. If you truly want to eliminate short rests, you could just give them the resources upfront the same way casters get all their slots. If you typically go 4-5 encounters before whatever rest allows a wizard to regain all slots, then give them double the resources at that point. If you go 6+ encounters between, give them triple. This simulates 1 or 2 long rests, at least for this purpose.

Personally my hope is that when they redo things for "Dnd one" they make is so the warlock and artificer share the small spell slot and spells know progression. I think the 2 classes have a ton in common in mechanics of invocations and infusions so to me thats what makes the most sense overall. 

How about instead of getting spell slots back times equal to proficiency bonus they get spells slots equal to their proficiency bonus?