They're a lot like your friend it seems, except another consideration for them is they often support their children by taking care of grandchildren when needed. They could still do this, to some extent, on a boat or in an RV. But would not be as available to do so, as they are now.
Large family dinners, holiday get-togethers would not be possible if they sold their home of course, but could be held at their children's homes.
I think your friend was wise to consider his alternatives if things didn't work out. Certainly they are carefully evaluating the move too.
One thing I see, after the great comments/advice, nothing is certain when a person(s) make huge changes in their lifestyle. What is certain is we're all growing older, and need to plan for this. Are there things we still want to experience, things we're no longer able to do, somehow share with others our success in the process?
Occasionally one needs to evaluate where you're at in life, what's coming down the road, and plan accordingly. That in itself is worth the time and effort to dream big.
You make very good points.
My suggestion is that they might try renting a boat or an RV for several months before making a larger commitment. And they should investigate retirement communities, which vary greatly in what they offer.
My mother is in such a place and loves it. She has a two bedroom apartment on a lake in Winter Park, which is an upscale city just north of Orlando. My mother sets her schedule and activities and usually fixes her own meals. Yet if she wants to eat in the cafeteria or needs minor medical help, they are in the building next door -- which is connected to hers by a covered walkway. A panic button system has emergency help from staff available at all hours. A full hospital is a couple of hundred yards down the road.
Continuity of care is provided, from temporary nursing help to hospice care. The retirement community has many organized activities, but my mother is healthy enough that she frequently drives to shop, visit friends, or see movies and plays. She sometimes even goes to lectures at the nearby college.