Both Kottke and Howe are in their late 60s. Musicians suffer from the same problems of aging as the general population and it can effect their performances. It's a rare musician who approaching 70 can play with the same technical proficiency they had when they were 25. I also think older musicians put technique in a different perspective from when they where young. It's important, but they embrace that there is so much more to playing than speed.
More than a decade ago I read an interview with Eddie Van Halen where he matter of factly stated that he couldn't play some of the material from the first few Van Halen albums. He explained that as he aged he just doesn't have the time or interest in playing the guitar 12-16 hours a day. Of course that's going to negatively effect his technical abilities.
