40 minutes SLOW. You can work up to 70 minute runs for more stamina but they should be easy, or the impact is too high for your sprinting. Instead of tempos do fartlecs with a stop watch, timed accelerations mixed with slow to moderate paced running for 20 minutes. Easy running and or drills for 5-10 minutes to warm up and strides after. You want the strides before any endurance workout and after any speed workout to add or keep range of motion.
also do shorter runs of 1-3 miles at a moderate to fast pace, first mile can be a warmup or walk. These are under rated for track speed.
basically you could opt out of the long runs and practice mostly 400 meter repeats with jogging intervals instead, but some lower impact and or higher quality road work could add to that.