I've had my DD just over 2 years. I hand wash it every week from ~late march - November, unless weekend weather is bad or if my weekend is jammed.
No it does not stay clean over the course of the week, but when weekly car wash time comes, I get the white gloves on. Sure it only lasts a few days, but a few days after that, it's made pristine again.
I wash mine regularly during the summer months and keep the interior reasonably detailed too but I'm not anal about it.