Do cats get more rambunctious as they get older?

That's odd. I've always had the opposite experience; my cats have always been full of energy and spunky as kittens but the older they've gotten the more mellow and generally lazy they've gotten. Perhaps the change in your cats has nothing to do with their ages but other factors; the new living situation, change in diet, or perhaps that was their real personality all along and it took moving to a new place for it to come out.