I have a friend in Idaho that shoots a 6mm-06 (very similar situation to the 6mm-284 in regards to erosion), and he used to joke that barrel life was easy to calculate: 1,000 rounds, then rebarrel. Yes, he probably could have gotten 1,100 or 1,200, or maybe even 1,300 rounds out of it, but when accuracy started to go it went fast, and he wanted to be spot on for long-range rockchuck hunting. A bore scope will tell you if your barrel needs to be replaced or just set back. If you are concerned with accuracy, rebarrel it. If you just want to switch to another chambering, setting it back will require completely removing the chamber area due to the large shoulder on the 6mm-284 being larger than standard head size (.473"). If you have to go that far, you might as well get a new barrel.
And not to short sell Hart, thay make very fine barrels and are the sweetheart of many benchrest shooters, but their barrels are high priced compared to other comparable quality barrels. Look at PacNor, McGowen, or Shilen for a replacement.