I bought my G21 in '95, since then, I replaced the recoil spring/ guide rod twice ( I'm not SURE it needed it, but each time I got a new set, I found it cheap at a gunshow.) I have had this Glock 10 yrs, and just in the last 2 months, I had put on a "extended" slide release. Thats it, it shoots to the same point of aim,(with the same CorBon loads) still chambers everything I feed it, and really looks not much different inside or out from the day I bought it.
And to think, I bought this Glock ONLY because the counter guy at a sport store really torqued me off.
If it was gonna' break for whatever reason, I think it would have by now.