Depending on the age of the child that is being potty trained you should take the child to the toilet every 1 hour to 2 hours.
An 18 month old that is potty training may need to use the toilet every hour or sooner while a 2 year old can usually hold it until around 2 hours.
So with a 2 year old you should take them to the toilet every 2 hours or if they seem like they need too sooner then take them sooner.
When potty training you're gonna have accidents especially if they are younger than 3.
Personally I believe that if you have to constantly take the child to the toilet and remind them often then they really are not ready to potty train.
I never potty trained my kids and most of my kids decided to use the toilet on their own after age 3.
Diapers are easier to change than dealing with messes in underwear, wet and poopy pants and wet and poopy floors, furniture etc.
A 2 year old can usually hold their pee for around 2 hours.
Most 2 year olds take around 2 hours to fill their bladder up before they need to pee.
So if you have a 2 year old potty training then you need to take the 2 year old to the toilet every 2 hours or so to pee.
If the 2 year old is still in diapers then they will usually pee every 2 hours and can usually go 4 hours with the same diaper before they need a diaper change.
My 2 year old boy only needs a diaper change every 4 to 5 hours depending on how much he drinks.
There's no need to change the 2 year olds diaper after they pee once because diapers can hold more than a few pees.
My 2 year old boy gets a diaper change at 8:00 AM and at 12:00 PM again at 4:00 PM and once again at 8:00 PM before he goes to bed and then he remains in the same diaper until the next morning.
So unless he poops he goes through 4 diapers per day.
I spend around $1.50 per day for diapering my 2 year old and I'm in no rush to potty train him.
That equals out to less than $50.00 per month for diapers.
As long as your 2 year old is peeing every 2 to 3 hours they are fine.