I guess the real point is … will you harm the watch. I mean that is the real concern. If the question do you need a winder because you are lazy and don't like setting your watches each the answer is obviously no. You do not need a winder. But on the other hand If you like keeping things all pristine and perfectly set by using a winder; will you risk damaging the watch. If the answer is yes you will damage it or you wear it out etc. I know certain machine need to be exercised all the time you cause more damage by letting it sit for months and then cracking for a few hours and repeating. Regular exercise in this case extends the life of the engine.