I'd try to avoid the "bleach-bottle"
boats (Sea Ray-style) for lengthy cruises and
live aboard cruising. They are great boats for a lot of purposes, but unless you are going for the really big girls, have a LOTS of
money to spend on fuel, and can afford to always have someone else keep those engines running in tip-top shape, I'd opt for a trawler or
motor yacht for this application. Find a good DeFever, Hatteras LRC, Symbol, Viking,
Grand Banks, Eagle, or similar.
You'll need to change you take on the interiors though. Those European designed layouts and decor are designed for that modern flare, but over time, the warmer appeal of the
classic trawler makes for a more comforting journey. I far prefer an aft
cabin for a calm night's sleep over the V-Berth configuration of the express cruisers.
Those boats can also be very rock-and-rolly at
anchor and don't handle large or following seas very well. They are designed to get you places in style and very fast. And burning many, many dozens on gallons of fuel in the process. They don't do slow very well. Sure, I drool over a 48 Sundancer when I see one, or a big Sedan Bridge, but for that kind of
money, there are far better options for the task you have specified.
That's just my opinion... Someone told me I was wrong once. :-D