I have to kind of agree with Greg here, even though I'm not a bump skier. My problem is that I am afraid of speed and don't feel as in control (mind you, I really only have 2 ski seasons under my belt). When my skis aren't freshly waxed, they're also slowed down a little. I know it damages the bases somewhat, but I almost prefer it this way. The one time I added on that rub-on wax last season, I ended up hurting myself the next time I skied... was a little faster than usual for me.
That said, in the past, we've always had our equipment tuned at least once per season. But not much more than that, and have never applied summer wax. My skis spend the summer in the apartment where the temps are fairly controlled, thanks to the A/C. No excessive dampness to rust edges or anything like that.