I have a three year old Glock 17 that I currently shoot weekly that has just over 45000 rounds through it. Ive replaced the extractor and its associated parts once, as well as recoil springs twice a year. Other than that, no issues. Other than a couple of recent cycling issues, which I attribute to worn out reloaded brass that should probably be scrapped, I havent had any failures that werent intentionally induced, or ammo related. The thing is like the Energizer Bunny, it just keeps going, and going, and .....
I also have a 26 of the same age that has about 20000 rounds through it. It gets shot about every other week. I change the recoil springs on it twice a year too. Other than that, and the intentional induced stoppages, no other issues.