Easy fix. Font of Magic spell slots fade after long rest or after 24 hours, whichever comes first.

Easier fix: Talk to my player about not trying to break the game.

— Dan Dillon (@Dan_Dillon_1) March 16, 2019

What is a coffeelock? Warlock/sorcerer with the “you don’t have to sleep” Invocation to cheese short rests and sorcery points.

People equate no sleep to not needing to long rest, so they stack up extra spell slots, refresh on short rest w/Pact Magic.

— Dan Dillon (@Dan_Dillon_1) March 16, 2019

Aspect of the moon does still explicitly say you have to spend 8 hours for a long rest. Whether you can short and long rest simultaneously is still something a rules lawyer can oddly poke at, but like you said, font of magic slots do explicitly fade with a long rest The coffeelock is built on just not taking long rests. Unless the DM institutes exhaustion for not taking long rests (which is weird with the disconnect between long rests and sleep), the character can build up tons of extra Font of Magic spell slots that never fade, RAW.

— Dan Dillon (@Dan_Dillon_1) April 1, 2019

Right but with the invocation it’s still wonky.

— Dan Dillon (@Dan_Dillon_1) April 1, 2019

Oh yikes. I never noticed that PHB doesn’t specify exhaustion rules for lack of long rest. I’ve just seen it as such a common factor that I assumed it was part of the core rules. Yeah, that’s either a house rule or pickup of the option in Xanathar’s Guide to Everything.

— Dan Dillon (@Dan_Dillon_1) April 1, 2019