A toddler can use the same diaper for 3 to 4 hours in the day and 12 hours at night.
If the toddler is awake they will usually need a diaper change every 3 to 4 hours as it takes a toddler around 2 hours to fill their bladder up and then release it.
So toddlers wet their diapers every 2 to 4 hours and some toddlers will wet through the day in little spurts and then eventually have the diaper wet enough to change.
As long as you change your toddlers diaper every 2 to 4 hours you're doing good.
At night however the toddler can stay in the same diaper overnight and then you can change the diaper in the morning.
If the toddler has pooped then of course change it as soon as you notice.
You can leave a disposable diaper on a toddler for around 4 hours if they are just wetting the diaper.
But if the toddler poops the diaper then you should wait at least 10 minutes before changing the diaper to allow the toddler to finish pooping.
Then change the diaper because they can get a rash from the poop and if the diaper is wet it should be changed once full or at least every 3 to 4 hours even if the diaper is not completely full.
Urine turns to ammonia after about 12 hours so the urine can cause rashes and burn the toddlers skin.
But if the toddler is asleep you can let the toddler sleep with the wet diaper and it will be okay but during the day the diaper should be changed.
Disposable diapers absorb the urine really good to help keep the skin dry and they can hold a lot of pee but you still should change the diaper often enough.
I changed my toddlers diapers every 3 hours regardless if they were soaking wet or not and within 10 to 15 minutes of them pooping.