How many rounds before replacing AR15 parts?

[22+1]

I'm sure everyone knows this except me, but in trying to keep up maintenance on my rifle so it won't go down at a match, when should I replace the bolt/extractor/firing pin/recoil spring? How many rounds? I'm not unloading three mags through it as fast as I can, just normal 3 gun stages and some practice runs, maybe 3-400 rounds per month. I'm not having any problems just some wear on the bolt cam pin and a slight groove on it.

 

[Matt1911]

It took about 2500 rounds for my last extractor to round off enough to not be reliable. I always install Wolf extra power extractor springs so the spring was still perfectly good when I replaced the extractor.