It's not that cut-and-dry, mind you, human being simply don't sort that cleanly.* But there's definitely something revealing about it. The problem for a serious gamer is that, over time, you eventually get tired of the kind of class you usually play, and start to branch out.
At least, I think that's all it is.
But it could also be a signal of personality change. As life forces you into new roles, perhaps your self shifts a bit, and your class choice moves accordingly. If that sounds like an interesting idea, let me assure you that it isn't. It's terrifying. What if I wake up one day, and all I want to do is swing a sword at a guy? What if I don't want to sit back inflicting status ailments with my bow, or cast a buff on my teammates? *shudder*
*Except thieves and rogues. They are always troublemakers.