Hmm I never knew that. Technically thanks to Google+ I have two channels, but I never really use that Google+ one...
See what works for you. My channel used to be just about the game review show, with some lets play videos in between so the channel won't be dead in the time it takes to edit and make another review episode.
Now it kinda evolved into sort of a 'all things geeky' channel, mixed with game reviews, comics reviews, movie reviews, Nerd Block unboxings and so forth. So I guess see what works with you. Do you want several channels, each focusing on different things, or one mega channel?