Not too many if you have the time and they hold your interest. I belong to 3-4 and that is about all I can handle. But they tend to be bike model specific. RC51, ZRX1100/1200, etc. Even though this is a Monster board it is obviously more generally oriented than that. Ducatis sure but you are here and others... don't ever see anymore complaining about that.
Heck I show up to rides on more Jap bikes that I do Ducatis.
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Enjoy it all, why not?
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Yeah I've been meaning to talk to you about that
On-topic: Whatever works best for you.