Once a week everyweek, but sometimes a quick wash midweek to keep it looking spot on.
I've found the effort i put in for the past two months, whereby i did the full shabang, applying 3 coats of sealant and then a coat of wax every week after a wash for a month, has paid dividends as one good wash a week and it looks perfect.
Its all in the prep, sure Rich will back me up on that.
And for those who cant justify the need for buying a PC to do once maybe twice a year, the result i have got from applying everything by hand are, IMHO, excellent. Technique is the key not just having all the expensive goodies...
AceJon