Not as often as I'd like! I've not seen my tank lights on since Sunday and I'm not likely to until tomorrow evening! There's just so much going on!
If my tank were open top then I'd have my hands in all the time, pinching bits off, removing that pest snail, grabbing that floating leaf. As it is with the big Juwel lid I leave it until I've got a spare half hour to do everything.
Still I usually get my hands wet at least 2-3 times a week on the one tank.