The answer you seek depends on many factors, here are a cpl: regular & correct cleaning procedures, # of rounds fired and what type i.e. Lead alloy bullets at target load levels, jacketed rounds at 1000 fps, or full max magnums.
As to correct cleaning procedures...much of the wear on a rifle or handgun barrel comes right at the muzzle crown...sawing the cleaning rod back and forth across the lip there, will destroy the accuracy over time. The same holds true for revolver cylinder mouths, but to a lesser extent. These are not my views alone...Camp Perry Service Team armorers have stressed these facts over the years, and will not let their shooting team members clean a barrel without a bore guide.
Anecdotal evidence being what it is...one man's opinion based on his experience, I can say that I have 1911's that have more than 10,000 rounds through them and still hold excellent accuracy...that means in my case, less than 2" groups for ten shots at 25 yds, rested. Most of those rounds were Lead Alloy, but a goodly number were jacketed. A couple of my revolvers have similar load counts and exhibit an even better accuracy retention rate. It's a fact that I rarely shoot magnum or max loads through my guns...I save these rounds for hunting, and rarely, load development; just to see what the gun's capable of.
Wear patterns differ: revolvers shoot loose in the fore and aft region, and may lose timing as well, especially if they shoot a diet high in magnum, high pressure loads...gee whoda figgurd.
My experience with autos is predominantly with the 1911. I've had only one of my guns tightened over the years...frame rails and their mating parts on the slide and I've never had to replace a barrel. I've not messed with the rest after they were initially gun smithed for triggers and initial rail tightening. That's one out of a dozen or so here in my family...(sons and I.) We do have a cpl of S&W M41's and a short barreled Colt Woodsman Target, but neither has had enough rounds down the pipe to worry about...less than 5000 each would be a fair estimate. And we never clean the barrels on any .22 lr gun that we own..rifle or hand gun...we do wipe them down and keep the bolt faces and rail clean, however.
I can't comment on the newer plastic type frame materials...our experience with Glock and Sig limits our involvement..maybe some others here can help with that.
We do own collectively, two Colt Commanders with aluminum frames that have 3000+ rounds through each of them with no accuracy degradation, as does my #2 son's Beretta M92...over 5000 through that one with no accuracy or functioning problems.
HTH's Rod