Shouldn’t damage it in the short term as long as you are not getting any flickering pixels, lines, or distortion, all of which could be a sign that you are pushing it too far. Long-term, it produces more heat so theoretically might shorten the lifespan. I never had very much luck with overclocking monitors. I would always end up with artifacts in a certain application that would make me set it back to default. So I just bit the bullet and got a high refresh monitor a few years ago and no regrets.