1. More volunteer time at the dog shelter.
2. More reading.
3. More music playing, and finally really spend time on that violin that is currently a secondary instrument.
4. More time at "church" (read: Zen practice), yes, just like other old people.
5. Might finally have time to hike the Appalachian Trail, or at least large parts of it.
6. Finally find the time to sit down and decide what I want to do when I retire, 'cuz there's no way this list is complete.
All but #5 should be able to be done by all but the most feeble. I hope I live so long as to get bored in retirement.