Mary and Peter,
Thank you both for your comments.
For me, Aikido would really not have been a viable option when I was younger. I readily admit I lacked the patience and discipline. And physically, I am actually way fitter in my 40s than I was in my 20s.
As for the "emptying the cup", this is such an important concept to me I
wrote a blog post about it.
Finally, I think these two news stories are relevant to the discussion:
At nearly 80, he earns his black belt in Aikido
Daily Aikido routine provides strength, confidence after stroke
(Why do I sense that the above is some sort of subconscious effort to convince myself to finally take up Aikido?)