When an infant is properly hydrated the infant usually has at least 6 wet diapers per day.
When a toddler is properly hydrated they should have at least one wet diaper every 4 hours but some toddlers may not have a full wet diaper until 8 hours.
It all depends on the age of the baby or toddler on how many wet diapers they should have and how long is too long between wet diapers.
I babysit a 2 year old boy who is in diapers and even when he's properly hydrated he goes sometimes 3 hours before even peeing some.
So for him I sometimes only need to change him once in the 6 hours he's with me.
Usually he comes to me in a dry diaper and then by the time it's time for his mom to pick him up I change his diaper because it's full.
His mom says at most he goes through 2 diapers per day because he holds his pee in and does not pee that often.
Unless he poops then he goes through 3 diapers per day.
The more a kid drinks the more they will pee and the less they drink the less they pee.
Also summertime when they are sweating the toddler or baby will usually pee less.
So your toddler or baby may have less wet diapers in the summer than they do in the spring, fall or winter.
According to professionals dehydration in babies and toddlers is fewer than six wet diapers per day (for infants), and no wet diapers for eight hours (in toddlers).