"Assuming typical adventuring conditions and average luck, most adventuring parties can handle about six to eight medium or hard encounters in a day. If the adventure has more easy encounters, the adventurers can get through more. If it has more deadly encounters, they can handle fewer."
Terms like easy and hard encounters refer to the exp budget in DM book. They also suggest 2 short rests a day, less nerfs short rest based classes like warlock, more can make them OP.
Should they enforce this or let the players decide themselves(like baldurs gate)?
Off course should lower game difficulties get more rests(or maybe no restrictions at all)
