How often do Pro-fighters train? Amatuers?

[Gmork]

I remember going into one of his big fights back in the day, BJ Penn said something to the effect of: "I'm done with overtraining. So now I do BJJ 3/4x a week, cause that's my thing, and boxing 1/2x a week." He meant in a training camp getting ready for a fight. I was shocked at the time because my friends and I were training more than that and we weren't even fighters.