Ours died after about four years. Or rather it developed a degree of independence on whether to allow our cats in. I can't blame it for showing some discretion, they're a horrible pair. It was getting pretty worn so we bought a new one. Quite happy with them, we were hosting a daily (and nightly) all-you-can-eat buffet and luxury free hotel for the local cats beforehand. Plenty of fun to be had watching bemused cats outside the catflap until they figured out that the buffet and hotel facilities were no longer available.
Cats can squeeze through surprisingly small gaps so he should be fine unless he gets really fat.