About 2000-3000 rounds, depending on how hard you push it. Most have seen 2300-2500 rounds before a you notice a fall off in accuracy. I'm at 2200 rounds and still shooting sub 1/4 moa. I'm thinking it will be soon.
There are a couple of posts on here that quote both Boots Obermeyer and Norma as stating that the use of moly coating gets them to 8k or so rounds in the .260 before noticeable throat erosion begins.