Predicting barrel life is extremely difficult to do accurately for many reasons, most of them in the hands of the owner and how they treat the rifle as far as cleaning and shooting.
Take a 375 AM and shoot it like a high volume 223 Rem Varmint rifle and you will get at least 500 rounds of accuracy out of it!!!
Take the same rifle as use it for its intended purpose, which is long range big game hunting, and the rifle would likely last a lifetime for even serious big game hunters.
Average barrel life will obviously be somewhere in between these two extremes. To be honest, I have yet to burn out a 375 AM barrel so I can not give you a solid number.
I have burnt out several 338 AM barrels and that one will average 800 to 1000 rounds down the bore with big game hunting accuracy. I would estimate a 375 AM would get you into the 1200 to 1400 round barrel life pretty easily if you take care of the rifle and do not over heat the bore.
Again, there are so many variables its hard to predict or should I say impossible to predict, its much more in the hands of the customer as to how long the barrels will last.
Hows that for dancing around the questions. Ya might think I was a politician!!! Maybe not!!!