One thing to remember about practice time is that quality ALWAYS beats quantity. One of the common mistakes and misconceptions that I’ve noticed about practice among musicians is that lengthy practices have become equated to an effective practice. Personally speaking for a moment, I’ve seldom been able to muster and maintain the concentration and focus needed to practice for anything more than 2 hours let along be able to maintain concentration for MOST things past two hours.
So why is it that long practice is equated to successful practice routine?
For the same reason we equate long hours at the gym with a successful workout, there is an aspect of “I did work today” that goes into this. In order for something to feel like we did it to the point of improvement and beyond, our default go-to is to do it for a long period of time, often past the point that our mind is still as actively engaged as it was within the first 30 minutes.
The mind can only stay engaged at an optimal level for only so long. Our concentration and willpower to go through and stay with tasks are finite. Very finite. So by going through irrationally extended periods of musical practice, time when our motor skills are working alongside of mental and cognitive abilities, is wearing down your brain at a much more alarming rate.
Using the workout analogy again, fewer reps with more weight using proper form will always beat out using poor form with an irrational amount of weight for 3 hours and continuing to work out for the sake of working out. Frankly in that situation, you’re well past the point of stressing muscles so that they can become stronger – you’re now flatly damaging your body. The same applies to practice. Past a certain point, you’re not improving anymore – you’re just going through the motions.
So the moral is this: practice with achieving a goal in mind and once it’s reached, put the bass down. You’re done for the day. You achieved what you set out to achieve. With regards to time, most things can be achieved in at most 90 minutes. Anything longer than that any you need to reassess how you’re approaching the problem to begin with.
For more reading on this topic, check out this cool article discussing methods to develop a good practice routine for bass players.