I really don't worry about it too much. The slide sweeps take care of most of it. I do have one large slide that tends to hold a little water, so if it is raining a lot, and we can't wait, I'll raise or lower the nose until the water runs off, then bring them in.
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder