Do you have a need for overclocking? Are you not happy with its performance and want to get more out of it? Do you just like knowing that you have an overclocked system for no compromises?
If yes to any of those questions, then go ahead and overclock. It won't harm the card, it may just reduce its lifespan a little (not saying much since you'll probably upgrade from it before it dies). I overclocked my 1070 founders just because I could and saw some minimal performance gains.