As I've gotten "older" (in quotes, as I'm only in my late 20's) I can hold both more and less depending on the situation and environment. If I'm at home, I can go for five or six hours without going to the restroom. If I'm at the office, where I'm usually going to the pantry to drink water to pass the time, I'm usually going every hour or two. On long car trips or transit trips, I almost never ask to stop for a restroom break.
I think that social anxiety also plays a big role in my using the restroom, as when I'm out at events with friends or new people, I'm going every hour to every two hours pretty consistently.
As far as I know, I've always been like this. It's gotten slightly better as I'm taking SSRI's that help with my anxiety.