Fastec isn't selling the 44610 door handles any more

There are a number of them available on eBay, perhaps buy a spare now if you're worried? I have the 44610 on my enclosed trailer; it seems pretty robust and gives me no reason to think that it would fail. But, it is also significantly smaller than many RV door latches in use (the Trimark on my MH, for example); so you could likely replace it with a larger (different brand) unit without "filling" in a gap if it did fail.