And play in a band. It really improves your skill when playing in time with other musicians. And always try to mix it up with people that push your limits. The better they are the better your chance to improve your own skill set.
And when you're not playing your instrument, you should be listening to The Greatest Albums ever recorded. Right now I'm listening to Bill Evans Trio at the Village Vanguard. Yes I've Listen to This Record seven or eight hundred times already. So what? No that's Miles Davis LOL
As a natural drummer who started at age 3, I’d never picked up any instrument if it required 8-16 hours a day to become “fluid”. Even when I was at my best, an hour a day tops (not counting rehearsals) would keep chops intact and see improvement and ease.