I've found that if you're going to use a treadmill it's a good idea to give yourself a tempo.
I like to start with a 2% grade at about 8.3 speed, then after 5min up the speed to 8.5, then up to 8.7. After 5min for each of those speeds, I up it again to 9.0 for 2min, then drop the grade to 1% for 3min. Then up to 9.5 for 3min, drop the grade to 0 for a minute and up the speed to 10. I keep the speed there for a final minute during which i continuously increase the incline.
That's a 25minute run.