On the one hand, I'm guessing that your job is valuable to you because it enables you to enrich your life and the lives of the people you care about in precisely the manner you're currently contemplating. You may want to ask yourself, "Wait a sec, if I'm not taking my family cruising, what's the point of this job?" If you think that the action that will maximize your family's happiness is switching to long-term cruising, then you should grab at whatever opportunity you see to get started. Your current job is just a means to that end.
On the other hand, you take your family sailing on the ocean every year for four months? If my parents did that when I was a kid, I guarantee I would look back on those trips and remember them as special times spent with family. As it turns out, they did different (less expensive) things with my brother and me that I remember quite fondly. Point is, it sounds like you think your family is missing out on its best years, when really they're having great times and collecting some long-lasting memories.
Sailors like to remind you that you'll regret the things you don't do. They are also notorious for sticking to what has worked reliably, and it sounds like your current lifestyle is working out well for you.
Also, you haven't said whether or not your enjoy your job. That would be a big factor for me.
1972 Catalina 27