If you're crazy enough to consider cleaning it so often.. go for it. I tend to wash once a week or so on a white because of the exhaust dripping onto the rear aero kit and that's already a chore. If I'm going to break out the solvent, may as well spend another 30 mins to do the rest of the car right?

__________________
'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr