You know, I've owned my 250 SL since 2007. I don't think I've ever washed it. Polished, glazed, waxed when got the car (I think, it was pretty nice) and detailed as needed through the years. California duster in between details with Griot's Speed Shine. Sure, I take a hose and wash the wheels and tires with brake dust and all, but not the whole car. Nice damp or wet rag to the nose if the bugs are bad to loosen them up and remove (right away) and then a detailer. Same with the rest of the car if I feel it needs a more liquidy wipe down. Water is the enemy in my opinion and less is more. It goes places where you may not want it to or see, and does its magic over time. In fairness, my 250 is out on nice days, never in rain, not on crappy roads. So, my protocol does not work for everyone, but does for me.
Pictures from 2007 when I got the car and 2 years ago in the upper garage when it was the 250 SL's turn to be driven that week. Gets maybe 500 miles/year of driving.