I recently broke the trigger spring on my one Glock 17. That was at the 89,000 round point, and the gun was still working with it broke, as long as you held the trigger for reset.
The only other springs I really had trouble with, was the RSA with my Kimber Ultra Carry. It seemed to need replacement every 250 rounds or so, and the gun never really worked right with the new assemblies installed, but it did run a little better.
I change the RSA's on my Glocks I shoot regularly twice a year. Theyre cheap enough, so why not.
I guess Ive been pretty lucky over the years with breakages of any type. The only ones I remember are the Glock spring, an M1A firing pin, the roller retainer plate on my MP5. All were high round count guns, and the Glock and M1A also had a very high dryfire round count.
I did have two guns fail due to, or related to, ammo. An M1 that slamfired, and a SWD M11/9mm SMG that had its top half start to come apart due to hot SMG ammo.
Considering how many rounds I usually fire a year (and that doesnt include dry fire, which is multitudes higher than my live round count), and how many over my lifetime, thats a pretty good record I think.