(This doesn't usually work for modern D&D, since combat turns are only six seconds and combat is more complex; a combat may take an hour to resolve in the table, but only one minute has passed in the fictional world).
Recently, I've been hearing about "real time downtime" or something similar (usually called "1:1 Timescale" or something; Jeffro Johnson has been talking about this recently, as have some YouTube channels). This means that if you spend one week (or one month, etc.) between sessions, one week has passed for the PCs, allowing them to heal, research, rotate characters, etc.
These are both interesting ideas that I have not tried extensively.
This post is about a similar idea, that I haven't heard elsewhere (AFAICT).
Old school D&D has strict rules governing how long exploration takes: one exploration "turn" takes 10 minutes and allow moving 120 feet (for an armored PC) or searching through a 10 x 10 square (or something; I do not remember the exact numbers).
This is a simplification. It should be obvious that finding a key on the ground of an otherwise empty, featureless room is faster than finding it in a chest full of objects.