Legally it's not a problem, as long as you own or rent a slip or a mooring. Thousands of people do it for weekends and longer all summer.
My parents went to their boat every Friday night from May to October for at least twelve years. They usually came home on Sunday night, but during there summer vacation they would spend a week or two there.
They started off with a 19' cuddy cabin in Back Bay and moved up to their "huge" 22.5' cuddy at Melvin Village. Eventually they ended up at West Alton Marina and stayed there until my Dad's health gave out. As you can guess with a boat that size, usually it was just the two of them. My sister and I would spend a weekends on the fold out seats. As we were teenagers, we outgrew that pretty fast.
This season will be my first, with my wife, at Mountain View. We have no kids and no animals, plus we're getting a bigger boat than they had. My generation is a little wimpier than they were.
You said year round, as far as I know that's impractical on Winnipesaukee. In theory you could have dock bubblers or something to keep your slip ice-free, but it's not going to happen.
BTW If you decide to do this, you should seriouly consider buying the boat on the lake from a dealer that will get you a slip. Slips set up for overnighting are not always easy to find.
Just to get a feel for what it's like check out
www.mvyc.biz or
http://www.spinnakercoveyachtclub.com/
I think the rules are on the sites