Hello and welcome to OSM!

AEDs are very important so any verified additions are welcome; for details on availability to the public and at what times there is no general guideline but, as far as I'm concerned, I try to narrow it down to avoid someone wasting time looking for an AED that is not available at that time of year. For example, for an AED located inside a school/hotel I generally try to add the estimated opening hours of that school/hotel. 

If unsure, I suggest you to just add the emergency=defibrillator tag and let other mappers to (sooner or later) add the other details. 

Good mapping,
Marco.