I've replaced my valvecover gasket a total of 1 time in 5 years. During that time, I took my valvecover off countless times for valve adjustmets, headgaskets swaps, etc. I didn't change the gasket until a couple months ago, and even then, the original one was still sealing fine, but I just thought it was a good time to use the new one I had lying around. As long as you apply some permatex or hondabond on the sharp corners of the gasket where it goes over the cam seal, it'll seal fine. If your gasket is pretty old, then consider changing it. Otherwise, I'd rather not spend the $6-12 everytime I take my valvecover off to tinker with something.