Here's a new idea has cropped up in lessons. When you're working on some technical etude, there's a range of tempos (tempi) that I refer to as the "bad middle."
What's the bad middle? Not slow enough for things to sink in and not fast enough to really stretch your technique.
I've started suggesting to students when they are working up something like a Kopprasch or a Tyrell that they should think of practicing either at a really slow, deliberate speed or lock those seat belts and go for it.
Why do we practice technical etudes? Well, to build our technique. If that's the case, think of using the etude as a tool to make you a better player.
You can learn a lot from playing a Kopprasch very slowly and sweating the details. You can also learn a lot from really challenging your personal speed limit.
When thinking of your practice tempo choices, think about that "bad middle."