For whoever the "average" (industry rated) owner might be, either the M3913 (and variants) or the P239 would probably be a fine choice, and probably a "lifetime" pistol.
As someone who has been through the S&W 3rd gen pistol armorer class a few times, and who has helped support upwards of over a thousand early 3rd gen and later production TSW's (combined), I've not had to do what I'd consider to be a lot of repairs on the guns.
I recently had to replace an extractor on a mid-2000's production 3913TSW which had some chipping on the hook's edge, but that was only because I saw it during an inspection. The owner said the gun was running and functioning just fine (and it was dirty, of course), and he'd not noticed the chipping. Probably wasn't wearing his reading glasses when cleaning the extractor, I'd guess. He's not been keeping a running tally of his rounds fired, but said he shoots the gun almost everyday on his own rural property "range". He's a retired LE firearms instructor himself, and estimates he's probably fired somewhere around 15-20K rounds through that just that gun (he owns and shoots a lot of them).
That's not unusual for 3rd gens, though, meaning to feed/extract/eject normally when extractor chipping may start to occur. I was once told by an armorer instructor (who was also a retired cop, firearms instructor and gunsmith in his former life) that a rough thumbnail estimate for the service life of a 3rd gen extractor might be at least 10K rounds, although he had some competition guns that had run twice that long without repair (both 4003TSW's, if I remember right).
I've had to replace a chipped extractor at just about 12K rounds fired in one of my issued early production 6906's (fired by me, but it had been previously issued before I got it), but that gun had the older style extractor in it.
I've had to replace fewer broken ejectors, but I started the practice of replacing older ejectors (short-tipped, with the sharp angled corners on the bottom) with the newer revised ones when I did have to replace a chipped extractor in an early 3rd gen gun, as the ejectors are one half of the "pair" of hard-working ejector/extractor partnership, especially in older, well-worn guns. Also, the revised ejectors have longer tips, which helps with faster ejection (especially when hotter loads are being used), and the change of a sharp angled corner to a curved corner (bottom of ejector tip, where it merges with the body) was done to help prevent a possible stress riser.
I've can guesstimate that over the years I've probably had to replace maybe a dozen chipped extractors in older 3rd gen's, and that's out of close to 500 older models that saw upwards of 15-20 years of service, and the TSW's that replaced them for several years before we went plastic.
Another guy used his early production 3913 for a lot of weekend competitions over what he said was more than a 10 year period (if I remember right, as that was a long time ago), and it needed a new extractor, drawbar and hammer. He'd chipped the extractor and worn down the notches on his hammer & drawbar (skips-DA issue was occurring due to the hammer/drawbar tolerances, which is why he brought it to me).
I've done a fair amount of shooting with my own 3rd gen 9's, .40's and .45's, and they've withstood years of frequent usage as training, off-duty and now retirement guns (and have still seen training/practice/qual use even in my retirement).
When I first became a 3rd gen armorer we had a very modest number of repair parts (I'd call it stingy). As it was repeatedly pointed out to me by the then-head armorer, though, that was because we didn't need many of them. It wasn't unless someone did something dumb with their gun, like not loading the chamber from a magazine, but dropping a round directly into the chamber and letting the extractor slam forward out and around the case rim, which could eventually damaged the extractor's hook. Or, trying to detail disassemble their issued gun (without approval, of course), and losing some parts.
It wasn't until some of the guns started edging upward to the 15-20 years in-service (and subject to the abuse of some cops

) that we started to see some worn out or damaged (by use) parts that require replacement.
I've stopped worrying about wearing mine out.
I've probably seen as many damaged, broken, defective or simply worn out parts on Glocks. Extractors, RSA's, some plastic parts, tweaked LB pins, worn out springs, etc. My own G27 had the FP and trigger bar engagement wear itself out-of-spec (meaning dropping below 2/3's engagement) at close to 14K rounds fired, while my older G26, similar used and having seen as just much shooting (with a lot of +P & +P+), still has great engagement. (But .40's are harder on guns than 9's.)
Most people probably won't shoot their guns long and hard enough to wear them out. An occasional replacement of a recoil or mag spring and they'll probably be good to go.
Hell, I remember when a "torture" test of a K-frame or a Colt Commander was considered shooting 5K rounds through them.
