Why waste tube life during "burn in"? When is that over? Who even knows? How bad can it sound? Just play it and listen. If you must leave it on when not listening so be it. Hifi is supposed to be for enjoyment so enjoy it to the max always. You don’t need advice from strangers to do that. It's always a good idea to have spare tubes around because you can never know for sure when a tube will go or start to develop issues that might be heard.
