OK, they aren't actually Commodores, but corralling the Berlinas didn't sound as good. I usually wash them once a week. It has been illegal to wash cars at home for that last few years using tap water, so the grand I spent on a water tank has well and truly paid for itself - plus I hate commercial car washes.
I wash them on the front lawn behind the fence to water the lawn as well. Based on how the water wasn't beading well, I'm due a polish.
For those who don't know, the sedan is a 2002 Holden VY Berlina, 3.8Lt L36 V6, dual fuel (gasoline/LPG) with 17" Holden International wheels. The wagon is a 2003 Holden VY Berlina, 3.8Lt L36 V6, dual fuel (gasoline/LPG) with 17" Holden SV8 wheels. We've had the wagon since May 2004 and the sedan since December 2006. The wagon has done 190,000km and the sedan has done 170,000km. Only non-service items have been a battery each and a radiator in the wagon.