In or Out?

This contraption, which looks more like the outcome of a Scrapheap Challenge, is the boat lift at the marina. The last time it embraced my boat was about a year ago when Henry was hoisted out and wheeled into the shed so that we could re-antifoul her.
Opinion (including my own) varies about how frequently a GRP cruiser should be lifted out, and for how long. When I had the Beneteau on Windermere I took her out of the water every winter, as much to comply with the insurance as anything else, but I know several people who keep their boats on the lake for two years at a time. When I bought Henry, her previous owner, Mike, told me that she was lifted out every few years, but that she had not been on dry land for four years.
I am sure that the osmosis doom mongers would say that anything less than six months out of every twelve on dry land is asking for trouble, but I have become fairly sanguine about the possibility of an old GRP hull having the odd blister or two. In fairness, GRP canal cruisers tend not to sink from osmosis, and in any event, it has been suggested to me that every GRP boat has suffered a certain amount of 'wicking' and as long as the blisters are smaller than dinner plates there is nothing to worry about.
Incidentally this was from someone who was trying to sell me a boat at the time, so no vested interest there then.
My own apparently casual approach to the whole issue is supported by the surveyor's report on Henry, which despite her lack of time out of the water since 1980, described the underwater hull sections as being 'in excellent condition'.
And that, since I greatly enjoy using her all year round, is good enough for me.