Pistol barrel life/wear question

I’m building a Noveske diplomat clone, and I’ve had a few folks talk about a shorter barrel life with a 7.5" barrel. For the life of me I can’t figure out why this would be true. Could someone shed a light on this for me?

I get that it’ll be rougher on the gun with all the unburned powder entering into the upper receiver, but I can’t figure out why the barrel life would be lessened.

Thanks ,I am just curious.

What kind of barrel life should I expect on factory ammo?

I think around 15000 rounds