I don't know about it being good for you, or even that it comes on gradually. I've got what I believe is a bad case of it, but it's in my left, non-playing arm. It feels just like people describe tennis elbow - it's on the outside of my left forearm, right up to the elbow itself, and even lifting my arm, I can feel a twinge of pain. Gripping anything hurts like hell. I can't imagine being able to play tennis if this were in my right arm. By now, you may be wondering how I got tennis elbow in my non-playing arm. I think I got it from doing "skull-crushers". Also known as "nose-breakers", "french press", and "lying triceps extensions". I had no idea it was doing anything to injure me until it simply started hurting real bad...been that way for almost 2 months now. It makes it really hard to work out - not being able to use my grip effectively makes so many weight-lifting exercises very difficult.
Ok, enough of my whining...just thought I'd share.