I found this interesting quote from Legato master TQ: "Once I had these exercises under my fingers I stuck with them for around 6 months trying not to speed anything up at all. I am firmly of the belief that if you practice slowly enough for long enough, the muscles and brain learn the required motor skills in a sub-conscious way and the technique becomes ‘easy’ for you. At this point your creativity takes over and the technique has become part of your repertoire. One thing I have found is that once the technique is in place at this sub-conscious level it really does feel easy and the speed is just a by product of that ease. One of the most important things I’d like to stress in this tutorial is to keep things slow and be patient – your fingers will know when the technique is ready and one day you’ll find yourself using it as naturally as you do with driving, riding a bike or cleaning your teeth! Patience and dedicated practice is the key to success. But then you knew that already!" This was in regards how he developed his legato chops. So, again, you might feel I'm cherry picking people who practice slowly but the fact remains that most if not all people with incredible technique says pretty much the same thing - Slow that shit down!