I'd be more concerned with wearing out the screws and the outside connections by taking the antenna off every week to wash the car, rather than just leave it on and let your warranty take care of any problems (that part would be "radio equipment" and not "trim.)

I've been washing mine since December with nary a problem. Acutally I didn't even consider taking off the antenna, since it's flexible. AND it is a lot easier on the top of the car than my Civic, which gives a nasty WHACK-WHACK-WHACK as the jets from the automated car wash beat the antenna mast against the top of the car. (note to self: pull in the Civic's antenna BEFORE putting it through a car wash!)