There is not so substitute for practice, but you can over-practice. This induces tiredness, muscle and tendon strain (RSI) and actual deterioration of skill, as well as loss of interest.

If you do want to practice 30 hours a week, the beginner will have to build up slowly over quite a long period of time.

If starting to seriously increase the intensity of training, you should have regular rest breaks to allow the body to heal or you will end up with serious problems.

Robin
Sports Trainer Level II Certificate
Australian Sports Medicine Federation.