On nights/days I don't have a gig or rehearsal, I'll usually go about an hour of intense work on some aspect or two of playing, such as range, multi tonguing, phrasing, etc. That's solid playing time, and that's about enough. I'm probably not getting much better doing this, but I don't think I'm getting any worse, either. There are other things more important, such as family and my day job.
I can't imagine having a horn stuck to my face for 4-6 hours a day with any regularity (I have played some 4-5 hour days, though), but I guess that's why I'm not a pro.
