Keep the barrel cool and clean and it will last a long time. Much has been said about the 270 WSM being hard on barrels, I have not seen this to be true when they are cared for properly.
As mentioned, keep shot strings to 3 rounds and clean bore every 40-50 rounds and you will be amazed how long the barrel lasts. Take the rifle out varmint hunting or do alot of paper punching in a hurry and you will burn up alot of barrel life.
I always tell my potential customers that "HOW the rifle is used and cared for is far more important that what the rifle is chambered in"
Most of the wildcats I have designed and build rifles make the 270 WSM look like an pip squeak. Of course it is not but again, my point is that how you care for and use your rifle is far more important then anything else.