Yea the silicone grease won't last as long as as required, Im just looking at one coat to do all winter with out re aplication.
I've used a product called dynax by Bilt hammer before although I've run out it is basically a thick spray grease wax that is self healing eg if a stone hits it it will recover and protect again and it does last through out the winter with perfectly protected coilovers underneath the only thing is it's brown and and a bit off a pain in the ass to remove in the summer.
Anyway I've sourced some heavy duty lithium grease so I'll give this a try this year
cheers !