Kirk Hammet surfs. I don't know about well, but he certainly qualifies in the music category. Like most things the amount of time to become truly great at something makes it hard to become really proficient in other areas.
Skynyrd spent summers practicing in a shack outside of Jacksonville where they'd play for days on end
The Beatles spent time in Hamburg where they played all night every night.
The Stooges lived in an abandoned house in Detroit figuring out how to be a band.
Eddie Van Halen spent weekends in his bedroom with a six pack and would play guitar all night while Alex went out in Pasadena trying to score chicks. And Eddie was already an accomplished pianist at that point.
Hendrix and Stevie Ray Vaughan pretty much lived with their guitars.
Fook 10,000 hours. These guys got their 10,000 hours in a summer. On the other spectrum I recall watching momentum generation and it seemed like half those guys came from broken homes or were latchkey kids. I'm sure there are guys on this forum that rip, but I'm also sure if they bothered to think about how much time they'd spent in the water over their lives..it'll be quite a bit.
It's really hard to be truly accomplished at anything, let alone two.