I don't think you need exotic gear and a mega wallet but IMO 50 feet
is the maximum that an older couple can handle themselves without
help, not to mention that the whole thing becomes way more expensive

I tend to agree. My wife and I are presently living and cruising on a
50 footer. I wouldn't want to handle or maintain a boat much larger,
and frankly don't see any need to, unless you have professional crew to
house or a large family.