I also have an R9, I got it about 8 or 10 years ago, maybe more. I can't count how many thousands of rounds I put thru it. With a quality springer like the R9, I do not think you could wear it out. It only seems to get smoother. I believe that Beeman would always be able to repair it if you needed, and I would think that any good gun smith could replace a main spring in it. If I recall reading some air gun enthusiests used to install their own main springs. I think the got them from Marconi? There was some person that used to sell tuned parts for the popular models.
They can last the rest of your life if you take care of it. And the most important thing to do, is only oil it SPARINGLY. Like 1 drop of beeman oil in the chamber a year or every 5000 rounds. I think that was what was printed in my Beemans manual.
I just ordered a Benjamin 392 for nostalgia. I still have the B392 I had since I was 8. I'm 48 now. My old one leaks and I dont shoot it, but I bet if I replaced the seal, it would work.
I think that is one of best things about airguns. They keep going and going.
Get an R9, you will love it.