I really think that you have to work them every other day. I knew a guy that was a body man and mechanic, he never touched a weight but had huge forearms. Grab a screw driver and put in about 50 screws in a wooden plank, tell me how your old forearms feel after that, they will be on fire. It all comes down to function, if you use the muscle the way it was designed to, it will respond. IMO