Back in Sept '90 I bought a used Glock 17, it's an early first gen.
Now, coming up on 26 years with her, I'd like to tell you a little about her.
I keep extensive notes on my firearms.
Over 30,000 rounds from various manufacturers including +P ammo and reloads.
3 jams (that's right 3!) one was due to a low powder charge in a reload
6 FTF (failures to fire) 3 or 4 were reloads, so probably my fault
What I willingly changed:
The sights (shiver), Glocks have 'slightly' sub par factory sights, She has had Trijicon Night Sights for about 5 years, A SOLID improvement.
The slide stop. For the past 4 years she has had a Glock Extended Slide Stop Release, I really only got this because friends were telling me it was SO MUCH better, My opinion, Meh. If I decide to switch it again I would get a Vickers Tactical Slide Stop. IMHO, much better but I'm not running to get one.
The Final change.
The recoil spring was getting weak, so I had to get a Glock Guide Rod and Recoil Spring Assembly. That was the ONLY necessary replacement.
Oh, some people get grip sleeves. I use a piece of a bicycle inner tube.
Here's hoping for another 26 years.