Normal LitterBox Visitation??

How many times a day is "normal" for a cat to visit the litter box? My 8-year old Vinny will usually pee once, MAYBE twice a day, and poop only once. Sherman, my 1-year old, in the meantime will pee 3-4 times a day and poop once or twice. Is this normal for both of them since they're different ages? They both eat the same food and same amount of treats each day.

I think for the most part its not the number of visits to the box, but changes in that number that you should watch for. If their litterbox habits haven't changed recently and they both have good bills of health, I don't think there would be a problem.