For myself it is the hands-on work I find most fulfilling unfortunately. I have some sort of brain worm that makes me want to practice all the new things at home/weekend if work isn't letting me. I'm sure it'll burn me out at some point, but to paraphrase a famous creep: I keep getting older, my brainworm stays the same age.
Within my power I try to do that with my directs, making sure new interesting things are cycled in so their CVs become stronger. But me, personally, I've had really bad luck with this. I always had to study on the weekends for something that either isn't used in my company or someone else jealously guards because it's hot on the market.