Hmmm... after reading this thread it seems that the yacht world must be a bit different than the house boat world. We are just talking about a basic time share here which is VERY common in house boats at many vacation
spots around the country.
In my experience, they work well on older boats and not as well on new boats. Older boats have typically already been pretty abused. A bunch of kids
jumping around and getting things wet and dirty isn't a huge deal. Everyone just cleans things up really well when they are done. Maintenance
is expected on an older boat too.
New boats are a different story. Many share holders want it to look and feel new for quite some time. If they are only getting 3-6 weeks of use out of it, they don't want it to look like a 5 year old boat after just a year of use. To some owners it will feel like each time they come out on the boat something new is damaged. This can be very frustrating.
Also in my experience, there is always one couple (sometimes two) whom are handy and clean. These people spend A LOT more time keeping up the boat than the others who simply enjoy their time and clean up a bit before they leave. On an older boat this hasn't seemed to be as big a deal, but on new boats I would write it into the contract
to get it professionally cleaned and have professional maintenance