Re: HOW LONG DOES 243 BARREL LAST???
More details are going to be needed to give you even a remotely accurate answer.
What has your firing schedule looked like? Long, fast strings of shots, or slow and with time to cool?
What do you shoot through it? Do you hot rod your loads or run them on the mild side?
Heavy bullets or light bullets? Fast powder or slow powder?
High quality barrel or factory job?
All of these things and more will have a direct bearing on how long your barrel will live, and even knowing all of these things it is still impossible to give you a precise estimate without having someone with a bore scope look down and actualy check it out.