Depends on how you use it. If you shoot 20 rounds in 5 minutes and do that every couple of weeks it will last a few hundred rounds. Getting it hot and continuing to shoot a bunch can be detrimental to the throat. Think of prarie dog hunting where you might shoot 100 rounds of high pressure, high velocity ammo in a half a day. THAT is what will "shoot out" a barrel. The 7mm Rem Mag is not particularly known for burning barrels partially because it is not really a varmint cartridge adn does not get shot like a varmint cartridge.
In life, strive to take the high road....It offers a better field of fire.
"Robo is right" Fuzzball