Springs weaken and need to be replaced. Some shooters swear they can feel the difference around 4-5000 rounds. Probably 10-20k and most of us would want to change the spring just because.
Metal that gets a pounding will harden (work hardening) and then crack. 50,000 to 500,000 cycles. Depends on the whole package working as designed and the design being worth a hoot. Also, as others have stated, running a steady diet of +P+ WITHOUT upping the rest of the system to account for the more energetic recoil, will make it fail sooner to much sooner.
But the guy that said 10,000 and it's worn out -- Brrrrrappppp! (sound of a raspberry or "Bronx cheer". Now if he shoots in mud puddles, stores it in rock salt and never cleans it ---> then he may be right!
