I think it depends a lot on your own definition of bored, and if playing a session when bored really gains your focus and interest.
Of course, if you're good enough and play games that you can kind of autopilot a bit in, you could certainly be making a good decision to play bored (more winning volume than you otherwise would have), but I would imagine that playing when bored often means uninterested for many players and can be a bad thing for plenty.
I personally play poker when I want to, so I wouldn't call it boredom. I don't think I've been bored in years, though my definition growing up was always "I don't know what to do, I'm so bored." There's always something to do these days, work, sleep, exercise, games, television, sports, dogs, friends, girlfriend, food, other hobbies. If anything, there's usually a stack of things I'd like to get to that I never do (many, many books and movies).