I am a diaper lover and wear and use diapers all the time now and I stay in a wet diaper for around 4 to 6 hours depending on how much the diaper will hold.
I usually go through 2 to 3 diapers per day depending on the quality of the diaper.
If I'm wearing a good quality adult diaper I can usually go 6 hours between diaper changes and if I wear baby sized diapers I usually change the diaper every 4 hours which means I go through 3 diapers per day.
That is about the same amount of diaper changes a toddler gets in the day.
Most toddlers of 2 to 3 years old goes through a diaper every 4 hours which is around 3 diapers per day which is average.
So for a toddler you would need around 90 diapers per month for a 2 or 3 year old which is about what I go through per day and per month.
I have stayed in a wet diaper for 2 days before and it caused a really bad rash so I will never do that again.
I change after 4 to 6 hours at most to prevent a diaper rash.