> It actually is good for the brain, especially an old brain, to exercise it regularly.

I'm a big believer in that. Exercising young brains increases their capacity for learning later, and exercising old brains helps retain it. It's fascinating the way the mind works.

One thing I learned recently, though, is that using the same kind of brain exercise all the time, even if it's a rigorous one, has less of a positive effect than trying out different kinds of brain exercises. For example, a thousand games of FreeCell is great brain exercise, but not nearly as much as 500 games of FreeCell and 500 games of...I dunno, logic problems or Go. Even just new non-cerebral experiences can be good, because your brain is still analyzing and exploring fresh possibilities instead of just pulling from memories. Not that continued involvement with well-explored brain activities doesn't continue to have a substantial benefit, of course.

Anyway, this is almost unfortunate for a creature of habit, like me. I'm into a few things faithfully, rather than a lot of things now and again, but it also comes as the encouragement I need sometimes to plunge into new kinds of brain exercises.