The 264 wm is one of my favorite rounds. I'd have one myself if it wasn't for the belted cases. The thing that hurt the 264 wm was bad press and the introduction of the 7mm rem mag with it's capability to throw bigger bullets. Which made it a better all around cartridge for the one gun hunter.
Wear at the crown is a major culprit to barrel wear. Another is not taking proper care after use and during storage. I was told by two different competent gun smiths that barrels don't wear out they rust out. Tiny little spots of rust, not visible to the eye, form inside the barrel and corrode the bore. The bullets are shot threw these rust spots and drag the rust down the barrel scratching the bore. Another is putting the gun in the case before it cools down. Condensation forms, which forms rust.
It's not a good idea to shoot any barrel at maximum pressure constantly. But, it's nice to know it can be there if you want. If I have the capability to throw a 130gr bullet @ 3550 that doesn't mean that I have to. If I reduce the charge just a bit. I'll still get very good velocity without running at max pressure.
The most important point I'm trying to stress is. Long wizzbang cartridges aren't neccessary to achieve max performance. As an example. The weatherby's are long rifles with long cases. If you get a rifle with a short action that shoots a short fat round and lengthen the barrel so the length of the gun is the same length as the weatherby. You can have a rig that will perform as well as the weatherby. This would be true with the 270 and the 7mm in the new short mags. I haven't done any figures with the 300 as yet.
These new short mags are very versatile rounds. Rifles with short barrels for light weight mountain use to heavy long hard hitters can be designed around them.