Well, is nothing wrong in keeping on that if is running without problems and keep it cool, after sometime he will have to lower those clocks anyway. Funny though, this is the reason there are so people complain about their hashrate, so many invalid shares due to that. I have a rx 480 here which was 2155 for 4 years then for some reason it does not keep like that anymore, I had to lower to 2000mhz for it to be stable few weeks ago, but it has run for 4 years at 2155 without problems.
A big problem is throttling where it doesn't run at a constant temp. I saw the cards without adequate ventilation have fans failing before the others. Now I spaced them far apart so they have room to blow and they're running a lot cooler and stable.