First where are you located? Second are you staying in the water or hauling for the winter. There are many Beneteaus here in Toronto that are hauled for the winter. AFAIK
they don't do anything to the shaft seal. The water drains out. When you launch in the spring make sure you "burp" the seal to get the air out of it. If you don't it will heat up and fail. Also don't you just love having to change this seal out every 500 hours???