Better 'app' for barrel life: http://accurateshooter.net/Blog/barrellife2013oct.xls
The factors to account for in barrel life:
-Your precision with which to detect departure in barrel performance
-Powder heat potential
-Mitigating factors(like melonite treatment)
The linked spreadsheet here has a common and competitive 6PPC load entered.
This is a tiny underbore cartridge using a very cool powder in well cared for barrels, but it's shot quickly in grouping, at extreme pressures, and with precision that lends to immediate detection of issues. So it doesn't see 5-6000 rounds of barrel life like anyone would expect, it sees ~900 before setback or replacement.
If your expectation from a 6PPC was 1/2moa, well then you can't detect accuracy loss -that you never had to begin, and you might think your accurate barrel life is way higher than reality.
So in this aspect it's subjective.
Barrel life is too complicated for a single chart because the causal combinations possible run into many thousands. Just play with QuickLoad a bit to see this.