Well, I've been carrying a 4516-3, purchased LNIB for the last 12 years. I qualified with it twice a year for 9 years. Shot it in IDPA competition and at least once a month on my own time for many years. I would estimate it has a little over 6000 rounds through it.
I've only had to replace one broken part. A MIM mag catch that fractured like the cheap pot metal it was. I replaced it with a forged steel part and have not had a problem since. I HAVE replaced the dual recoil springs on that gun over a dozen times. Runs like a Timex.
I have a 3913, early production. Carried it for over 11 years off duty and to court on occasions. Qualified with it twice a year and shot it some on my off time and in two off duty gun matches. I'd estimate its round count at 3000+. No failures......ever. No broken parts.....ever. Did change the recoil spring regularly.
Also have a 4513TSW. My favorite carry gun. Been carrying it on and off duty for the last 5 years. No idea how many rounds through it as it was an LE trade in when I got it. I've shot the snot out of it. Easily 2000+ rounds. Nothing broken. Changed the recoil springs and didn't like the look of the tip of the guide rod, so I ordered a new one and replaced that. Are you seeing a pattern here?
If I were you, I'd stock up on recoil springs, buy 6 mags for your carry gun and carry it with no worries.
You hear one or three folks around here worrying about parts or encouraging new folks to not buy 3rd gen guns because the factory doesn't want to support them any longer. So that they can peddle the high profit plastic junk with the lousy triggers they now make.
I say buy a 3rd gen, shoot it, love it, maintain it. Good luck! Hope this helps! Regards 18DAI