I don't take lessons. never have. don't have my own drumset. play maybe once or twice a week, 30 minutes max. been that way for about a year and a half (felt like much less). the best part? I'm pretty good. =D
of course, you still have to have some semblance of musicianship - know what to work on. I may have only gotten maybe one or two 30-minute sessions a week, but while I was playing, I knew what to do. listen to myself playing, figure out what I'm not good at, and correct it. you can play hours a day, every day, for weeks on end, and you'll still suck, if you're just practicing the stuff you already know how to do.
now I'm gonna do that same routine with bass. 🙂
(oh, on a side note, I did buy a book, but it really didn't help.)
(another interesting note about meh drumplaying - I'm a righty. I play lefty drums. what the heck. yeah.)
(I can still play righty drumset just as well, though, it just leads to some awkward situations if I have to use the ride.)