COBrian is right. If the gun is made without a defect or issue, it's very rugged and reliable. I don't think it takes long to discover if something was missed by quality control, especially fire pins.
BUT other have had the factory sell them a fitted spare bolt and pin when they sent in their broken pins to be replaced. I will probably do the same, but I'm over 1k rounds without issue..
You should stock the following parts:
1. Spare action spring (EVERY self loader should have at least one spare since with use they WILL lose "power" and the action will take a battering)
2. Set of smaller springs - breakage/loss is the issue here
3. Firing pin, extractor, ejector with associated plungers, etc. I DID have a firing pin break around the 4000 round mark and have never used anything but brass cased .223/5.56 ammo
4. Replace handguard with a FedOrd or Choate nylon model. The original fiberglass ones chip and can crack in a drop. The FedOrd and Choate models also promote cooling better.
5. Rear sight screw set - I have had the screw that holds the assembly as well as the two that hold windage come loose, though haven't lost one yet. At bare minimum you need to use blue loctite on them if you aren't going to stock spares.
If you are using irons, I strongly advise that you pick up a tech sight to replace the stock rear sight.
Other parts can be bought for a comprehensive armorer's kit, but the fact is that you should be able to fix pretty much everything that is likely to go wrong with that.