Just like a baby or toddler who wears diapers and pees in them an adult should change their diaper every 2 to 3 hours or when it gets full.
You really do not want to wait until the adult diaper gets too full because it can leak which would cause your pants to get wet which defeats the purpose of adult diapers.
There have been times that we would be on road trips and when I got to a rest stop my 3 year old son would have wet pants and a wet car seat because he leaked through is diaper because he drank more and wet more while traveling.
So you want to change the diaper before it leaks which is every 3 hours or sooner depending on the capacity of the adult diaper.
The pee eventually turns to ammonia which starts to smell and then leads to rashes.