You flatter me, Giz. Don't stop(G)...
Slater, any of the Big Four pumpguns will likely last longer than we will. The 870 seems to be the one with the best longevity, but there's not many 500s, 37s, 1200s or 1300s that have been worn out, even to the point where retightening is needed.
Old pumps, except for a few POCs like the Noble, stop working from neglect and sbuse, not fatigue.
Between personal and professional use, I guess my lifetime total of shots fired from maybe 20-30 870s is around 50K. Of course, most were dept weapons, oft abused and neglected. I recall no glitches I didn't deliberately induce.
For general use, with a mix of high pressure and lighter target fare, my semi educated wild eyed guess is ANY of the Big Four will last 30,000 rounds if given a modicum of care and PM. If it's a target gun primarily, using nothing heavier than 3 dr, 1 1/8 oz, add another 10K. If used for Steel plate shoots, hog hunting, waterfowl, and other stuff requiring high pressure loads,maybe subtract 5K.If it's an 870, maybe double that.
In actual use, we'd have to fire off lots of shells out of any of these to render them useless.
Some like the 870, can be re headspaced by simply replacing the locking bolt with an oversized one, available from Remington for a few bucks.
QC varies not only from company to company, but over the time line also. Ithaca 37s are great pump guns, but some made during a period of tough times when the maker went into receivership/bankruptcy were rough, poor wood/metal fit, dull and streaked finish, etc.
New 870s, including the premium Wingmasters, have had QC probs, off center bores, looser tolerances, and so on. few of any of these probs seriously affect performance, and none safety.
What I'm trying to say is that durability is a non issue with the Big Four pumps.More important are fit and feel.
The McCRule:
Get the one that FEELS best....