Yeah, water pumps are funny things. Jake Raby, who used to post here frequently and has forgotten more about 986s than I'll ever hope to know, used to recommend a new WP every 3 years. That always seemed excessive to me
What I assume was my first one (I bought the car, an '01, in 2006, with 19k miles) went bad on me in 2011. So it was like 10 years old (at 58k miles). I just got around to replacing that one, proactively, in 2022 (109k miles) and it looked fine, spun smoothly, etc. But I was doing other cooling system work anyway and figured it only made sense to R/R the pump.
But the "funny things" part is that I guess sometimes they do fail within a much shorter time period—and it can be kind of a big deal when they abruptly crash and burn on you. So I would, with whatever authority and confidence I can muster
recommend replacing them somewhere between every 3 and 10 years...FWIW.
I have, on both occasions, used the genuine Porsche product and personally think that's the way to go.