If you're wearing diapers and have a wet diaper you need to or at least should change the diaper when it gets wet enough.
Usually you should go no longer than 3 to 4 hours in the same wet diaper unless you're sleeping then it's usually okay to stay in the wet diaper and change the next morning.
Adults skin is more tough than a babies or toddlers skin is so an adult could likely stay in a wet diaper longer than a baby or toddler could without getting a rash.
Babies usually have their diapers changed around every 2 hours and toddlers older than 18 months usually have their diapers changed every 2 or 3 hours depending on how often they pee and if the toddler or baby poops them the diaper should be changed immediately.
If I were wearing diapers as an adult I would change every 3 hours at most even if the diaper were not very wet.