I feel like the good marathon workouts often take a lot of time, for good reason obviously (it's a long race). Long tempo runs, tempo intervals, and obviously quality long runs all take time.
What are some good marathon workouts if you only have, say, 45 minutes or so and want to get in a mini-workout, say the day before a long easy run? 20 minute tempo with 10 min each w/u and c/d? Mile repeats? Any other suggestions?