You'd obviously get higher round count with not so hot loads. It's hard to put a number on it as everyone shoots a different variety of charges. Higher charges will accelerate the process. Just keep in mind both 243 and 308 run about the same charge but bore is smaller in a 243. Factory loads should last 4-5k rounds before accuracy goes south. Some people report as little as 2500. I understand some people may never even put 2000 rounds through a given rifle in their life