I have mine set to extra ball, but it's only one level, and I set it pretty dang high, too. I do this because I feel it's a kind of achievement and should you get to that replay score, you deserve an extra ball.
When I have mastered everything at the game's current difficulty level, I'll bump up the hardness and leave the replay score where it is, it'll still be harder. Then, when I've mastered the game at that level, I'll max everything else out to their hardest levels and still keep the replay=extra ball feature. When I master that, THEN I'll take away the replay=extra ball feature. At that point, I should be getting LITZ every game. Hey, it's all practice to help me get better and better.
Besides, it's my machine, I can do what I want with it.