Ditto @ 21 years! It's not work, it's a hobby I happen to get paid (well) to spend time doing (well). The field is sufficiently vast, with "new things" (that I can teach myself at 0 cost, not including time) "coming out" at an ever increasing rate that there isn't the slightest chance I'll run out of things to learn. Plus almost all of my "old knowledge" is still relevant.