I've had my soft top stowed for a few months while the hard top was on, and no shrinking occurred. Wetting several times a week does not seem like a necessity to me, unless to stretch (but search the archives for how to stretch a soft top in other, probably more effective ways). Meguiar's makes very good products to keep the window very clear, and then there's the old Ragg Topp cleaner & protectant to care for the fabric. I have found high-pressure water can clean up a soft top that has a lot of dust, tree sap etc in it, very nicely.
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic