Recently, I made a post on how to store ~180 damage using Magic Missile and Glyph of Warding, by using a combination of short and long rests to cast the Glyphs. Someone pointed out that you can only benefit from one long rest every 24 hours, so my plan that I had set up wouldn't work because of the rules. I wasn't aware of the specifics of all the things that were required, like Glyph of Warding not being moved more than 10 feet or the glyph being broken. I have come up with a better system and a few ways to get around the limitations of the things required.
Prerequisites: Level 15 Wizard, Glyph Of Warding, Magic Missile, Imbued Shivarran Birch Focus, Spell Refueling Ring
The best way to maximize glyphs cast would be this:
Cast Glyph of Warding (GOW for short) 3 times.
Take a long rest
Cast GOW 3 more times
Take a short rest, recover two 2nd level slots and one 3rd level slot with Arcane Recovery
cast GOW 1 time
Use the ring to recover a 3rd level slot
Cast GOW 1 more time.
In 17 hours, you can get 8 glyphs with second level magic missile on each. 2nd level magic missile, with the imbued wood focus, averages 18 damage. for a total of 126 damage of average, with no saving throw or attack roll.
The limitation of this is due to GOWs not being able to move more than 10 feet from their original casting location. Using Demiplane, and casting all of the glyphs inside of the Demiplane you create, you could put the glyphs on an object that you would take out of the Demiplane to use, like a lever that would, when triggered, target the nearest creature in a line in front of the user. 

Edit: I wanted to expound on it's uses. When given downtime, you could make this fairly easily and get into the thousands of damage given a few weeks. If someone ever pulls this off in a game of yours, something you could do is upcast Shield so a counterspell will likely fail to counter it.

The GoW must target either a single creature, or an area. If your DM agrees that Magic Missile qualifies (you can target multiple creatures, but don't have to), the GoW will target the creature triggering it with the spell. 

You could not trigger the glyph and direct the missiles anywhere. 

Also, if you move the GoW more than 10 feet from where you cast it, it breaks without triggering. Arguably, removing it from a demiplane would do just that.

You can upcast your glyph of warding and upcast your magic missiles to get more castings per rest and more damage output.

GOW says:
When you cast this spell using a spell slot of 4th level or higher, the damage of an explosive runes glyph increases by 1d8 for each slot level above 3rd. If you create a spell glyph, you can store any spell of up to the same level as the slot you use for the glyph of warding.

MM says:
When you cast this spell using a spell slot of 2nd level or higher, the spell creates one more dart for each slot above 1st.

As a 15th level wizard you have  the following slots:

 So...let's maximize this...

Start of day:
Cast a Level 8 GOW with a Level 7 MM inside (9d4+18)
Cast a Level 6 GOW with a Level 5 MM inside (7d4+14)
Cast a Level 5 GOW with a Level 4 MM inside (6d4+12)
Cast a Level 4 GOW with a Level 4 MM inside (6d4+12)
Cast a Level 3 GOW with a Level 3 MM inside (5d4+10)
Cast a Level 3 GOW with a Level 2 MM inside (4d4+8)

Take a short rest to recover 7 levels of spell slots.  (Arcane Recovery) - Recover 1 4th level slot and 1 3rd level slot.

Cast a Level 4 GOW with a Level 3 MM inside (5d4+10)

Use spell refueling ring to recover a 3rd level slot.

Cast a Level 3 GOW with a Level 2 MM inside (4d4+8)

Take a Long Rest early, and do all of the initial castings again:

Cast a Level 8 GOW with a Level 7 MM inside (9d4+18)
Cast a Level 6 GOW with a Level 5 MM inside (7d4+14)
Cast a Level 5 GOW with a Level 4 MM inside (6d4+12)
Cast a Level 4 GOW with a Level 4 MM inside (6d4+12)
Cast a Level 3 GOW with a Level 3 MM inside (5d4+10)
Cast a Level 3 GOW with a Level 2 MM inside (4d4+8)

End of Day.

Now in 24 hours you have cast 14 GOWs with various level MMs inside amounting to 83d4+166 damage (373.5 with average rolls).

If you dip wizard to level 5 and then take the rest in Sorc so you have empower metamagic you can make 10 of the MM castings empowered...letting you reroll your ones and bringing the average die result on a d4 up to 2.7142 for 66 of the 83 darts.  Lets you squeeze another 14 points of damage out of the combo.

Oh, but then you don't get as many spell slots back from arcane recovery...never mind...that doesn't help.

Oh, I completely forgot about upcasting. I also realized that instead of a demiplane, a bag of holding would work just the same if your DM allowed it.
It really is up to your DM whether or not moving between extraplanar spaces like a demiplane or bag of holding should count as moving 10 feet or more, even if it didn't move 10 feet in the conventional sense.