I like to think of myself as "still pretty fit", but, yeah, next year I'm 60. I really appreciate your point of view, and I'm still leaning towards the midweight Relay, even though I understand that I won't be able to keep up with my "full-fat" (in more ways than one) friends when they are...
One of the reasons my endurance isn't as great as these skinny kids (besides my age) is that I am somewhat of a power lifter. Kills the endurance, but my upper body strength isn't lacking. I raced motocross in my youth (45 years ago), so I vaguely recall what a heavy bike is like... shouldn't...
More or less narrowed down my choices to either the Transition Relay or the Yeti SB160e.
Transition Relay
+ lighter, more playful
+ stealthy
- started to hear about some issues with the motor
Yeti SB160e
+ More mature company & technology
+ high probability of more thorough development process...