My sail wasn't sliding very well on the mast so I decided to clean it up with some abrasive cleanser, rinse it off really well (chlorine not good), let it dry then put on some car wax. After I buffed it off it was slippery as heck and the sleeve slid on it really well.
I thnk that waxing the spars counts as "preventative maintenance" which is legal+ i have heard about doing that in a few books. When i bought my boat I also waxed the spars so I am fairly sure that we can do this