I have relatives that leave their boat in the water all season, private docks on the lake. Biggest thing is to protect the valueables, and protect it from the inclimate weather. Typically a nice cover will serve both purposes, keep untrustworthy eyes off the valueables and keep mother nature out.
When on vacation last month I left my boat in the water all week. I coverd teh boat every night. Biggest problem I had was ants. They boarded like little pirates, via the dock lines, and found plenty of minnow parts to eat. Pretty sure they started a northern branch of the family when I got home.
Edited to add this:
One faction of my gamily has a boat lift. When they are done using hte boat they lift it out of the water, still in the dock, just above the water. The pontoon stays in the water all summer, gets pulled out and put into storage for winter. While in storage the company gives it a tune up and preps it for the next season.
There is one Lake I fish with boat garages, with attached sports bars.
HOI Crappie Club
Where family and friends come to compete for a little more than bragging rights.
Quick, someone teach me how to fish so I can win this tournament!!!