Really? I've seen speculation as to their age, but from what I've read of the books my impression is that Jeeves is not that much older than Wooster. (I'm saying this not having read all of the books.) It could be that I'm influenced by the tv show, but I've always thought of Jeeves as maybe ten-fifteen years older than Wooster. The way Wooster describes Jeeves makes me think of someone who is still in their prime.

It is somewhat difficult to peg their ages, since time, the time-line, and age in the books are not always defined (nor do they need to be either, which is the beauty of the thing). I think that I can canonically justify J&W at being ten-fifteen years apart.