I'm going to second this one. A physics professor friend who taught me electronics when I was a kid is now "retired", as in still coming in to the university se

I'm going to second this one. A physics professor friend who taught me electronics when I was a kid is now "retired", as in still coming in to the university several days a week, but only to do the interesting things they want to, rather than needing to because their boss says so. One of the perks of academia. You can retire, but prevent boredom.