Greg
I am happy to hear you have done well with set backs - it's great when it works out like that.
I feel I need to add a little more to my posting above.
Over the last 5 years or so I have had probably 8-10 barrels set back and re-chambered, and it typically has turned out to be about a 50/50 situation, and for all that is involved doing set backs, setting up the rifle again, doing load testing and work ups with a set back barrel, those odds are not worth it to me (unless one is making a barrel up for fire forming, or some other type of testing where the best accuracy possible is not perceived as being needed).
I also start out with somewhat of a view "if it ain't broke, don't fix it" in that if I have a barrel that is an excellent shooter, I will keep it and use it until it ceases to perform (i.e. why mess with something that is 100% - it's like asking for trouble). You are correct, that by the time those barrels cease performing, cutting an inch or two off the breech end just does not seem to solve the extent of the barrel wear and tear. When I look at my Dasher and BRX barrels after 600-800 rounds, I see stuff going on a lot more than just 1" - 2" up the bore.
Typically what has wound up getting set back for me have been barrels that for one reason or another have not worked out well and are not being shot or used, and I am hoping to get a project going without having to buy a new barrel. Maybe that's why the odds turn out about 50/50 for me, in that those barrels were not known as being great to start with and maybe nothing will make them great (i.e. there's a little bit of "luck of the draw" with barrels, even the best).
"Throwing good money after bad" is most annoying and I have been down that road a few times with set backs, setting a rifle up again, doing load work ups and testing, and after a couple hundred rounds and a multiple trips to the range determined that it was all a waste (again). From that perspective, these days I am more inclined to take my chances with a new barrel.
Robert