WOW, Mully - your friend is fortunate to be doing this at 74.
My long time buddy is 74 is **** fit for his age; but, we had "the talk".
Surprisingly, the first time he ever listened to me - he made the switch to three wheels a couple years ago.
We both still have a blast, I breathe better and he can go all day, no problema - now, the night, - that is an entirely a different issue
I can see myself on a trike (prefer reversed) if it's got a Rocket engine in a decade or so . . .
Best Regards,
1olbull