I had my reamers ground for 120-150g nosler ballistic tips in the 7 STW with .030-zero freebore. Accuracy was bug hole with R#22 using the 120g and IMR 7828 for the 140g. As you can imagine, with such short freebore, accuracy lasts a LONG time. I have never got around to shooting the 150g.
My reamer was zero freebore, and we shot nothing but the 120g Nosler solid base lead tips at 3850 out of 26" hart 9T barrels with R#22....accuracy is still hard to believe, three shot groups in the 2's and very low 3's. Even fire forming Rem 8 Rem mag brass, three shot groups were in the 3's. Skip forward, the Barnes 120g TTSX and TSX are just as accurate, same load, seated the bullet deeper in the case.
The 140g Nosler C/T bullet were scooting along at 3600+, deer NEVER took at step.
If I hand known of the heat index of powders, I would have tried the H1000, N160 powders, with throats lasting longer than they have with the zero freebore.
So, you ask how long the barrels lasted, well, they are still running. Many in the family are using the 7 STW's, and with load development with the 120 & 140g Nos C/T bullet being so few rounds, we all just verify zero from year to year, hunt. 300-400 rounds ads up to a lot of years.
I keep good records on my brothers 7 STW with a 11 twist Pac Nor, 27" set up for 140g Nosler C/T bullet, and the bug hole load is at 3700 fps with IMR 7828, FED 215's, in a zero freebore chamber. At 235 rounds, he has .017 leade growth. His load development with the 140 C/T bullet was around 21 rounds total. He has killed 150 + deer with the rifle or more, I don't know that he has ever missed. Wild dogs (no collar) running deer are targets of opportunity, coyotes are a bonus. Brother put out a food plot from one stand at 500-550 yards....even the 120g ballistic tips at 3900 Muzzle velocity make them flop on the spot at those distances. We named the stand, "STW Stand".
I would guess that if you set the rifle up with a long throat for the 180g-195g bullets, that your barrel life would be less as big heavy bullets with slow burning powders, tend to cook throats.
Your shooting habits will dictate how long your barrel will last in a 7 STW and 28 Nosler. 1200 rounds on a zero freebore chamber is my good guess, and for guys that do not poke at steel, this is a lot of years of hunting. For a chamber with .220 freebore, then I would expect 600-800 rounds to give the very best service life with friendly bullet jump designed bullets being a bonus.
If a deer hunter was practicing shooting steel at ranges from 700-1600 yards, then it would be prudent to have two barrels chambered at a time. Figure out the dope(confidence) on the first barrel, then the second will last a long time.