I've talked to some drummers who seem to have a very hard time staying in shape on the road, including some drummers touring with high-profile acts that don't have to live on fast food every night.
No matter how much success you're having, you can't continue working together if you can't communicate.
Whenever Elvin Jones comes to Seattle I try to go catch him.
I guess by taking lessons early on, and really trying to play all the rudimentary stuff, and try to have it sound as good as my teacher. It took a lot of practice, which I enjoyed, and still do.
I try and stay limber, swim, run, ride motorcycles.
I always loose a little weight on the road, so I constantly have to be on top of my nutrition and hydration.