It's good to continue practicing. Adding new routines to acquire more advanced techniques is a good way to stick with it. I think the biggest problem with practice routines is one they become overly repetitive, and people spend too much time doing the basic stuff. 4 hours a day is too much. I personally only spend maybe a half an hour a day going through exercises and what not. Sometimes not even that but I always try to at least play for alittle every day. I eventually quit because I once had a similar grueling schedule and I used to force myself to stick with it until the fun was lost. Now I just try to have fun, dip into some exercises. I actually learned alot faster that way. Boredom and fustration is what hinders you from progressing, actually it can make you go in reverse.