When a toddler is still in diapers then they should have their diapers changed once they get full which is usually ever 3 hours or so depending on how often and how much the toddler pees.
Disposable diapers are very absorbent now that the toddler doesn't feel much if any wetness on their skin when the diaper is only half full of pee.
But when the diaper gets really full and swells up then the pee can be felt on the toddlers skin.
You don't have to change the toddlers wet diaper just because it's a bit wet.
But make sure you check the diaper every 2 hours or so to see how wet it is.
Once the diaper gets full and swells up and is squishy in your hands then it's time to change it.
You can however let the toddler sleep in a wet diaper as long as it's not on the verge of leaking.
But during the day the toddler should not wear the wet diaper that they peed in longer than 3 hours because it can start to leak and cause a rash.