Not sure if this is a good idea or not, but all I can say is it works for me ! I use my metronome quite a bit to help with my right hand speed (and no inuendos guys !) in a similiar way to interval training is used in most sports. Fairly simple - a gentle 5 min warm up by dialing in a tempo of 70/80 bpm, play quarter notes for 16 bars, play eighth notes for 16 bars, play 16ths for 16 bars. Repeat using a bit of variation for about 5 mins. Once your warmed up crank up the tempo a notch and repeat for 2 mins. And crank up the tempo a notch and repeat until eventually you can't keep in time with the metronome for more than 3 or 4 bars. At this point you need to change your intervals, say alternate bars of 16ths and eights. Note the tempo at which you fail and this is your target to beat in a week ! This is just a simple repetition exercise, but the metronome adds a measurable element to indicate your progress.