Re: How many rounds before re-barreling?
A lot also has to do with the round you are shooting. load up some of the small bore hyper velocity magnums and they will eat the throat out of a barrel in 1,500 rounds. Load up a mild shooting big bore and it will last ten times that. Another factor is how much you heat up the barrel when you shoot. A good day on the dog towns will have the barrel hot enough to burn your hands... Not good for barrel life... While a couple rounds down range with 20 minutes in between will prolong that life.
And the starting quality of the barrel will also be a factor. A crappy low cost tube will lose accuracy faster then a top quality hand lapped stainless barrel.
I would just shoot it till it gets to the point you cant shoot a group thats acceptable to YOUR standards. I am sure David Tubb throws away barrels that are more accurate then what comes out of some factory "custom shops"... but then again, he also has sponsors that supply him with new steel for free and needs that extra .0001" of tightness to win. Whereas you and I can get by with a 1/2 or 1moa rifle instead of his 1/4moa rifle.
I have a 308 with a little over 5,000 down the bore that has opened up a little from what it was new, but its still under an inch even on a windy day at 100 yards.
When is it time to rebarrel? It is up to you and you alone.