Hey Letsrun, I'm currently a senior in high school, and starting my track season.
Over the winter, I had planned to do doubles 3-5 times a week, and get up to a good 60-70 mpw. Unfortunately, an injury that carried over from Cross Country sidelined me for all of December. I came back slowly and am now back up to 45 mpw in singles.
I'm mainly focused on the 800, but will probably be running the 400 and mile occasionally as well.
What I'm wondering is that if I start doubling now, will it be worth it come April/May? One thing to note would be that I have never doubled more than twice a week, and the most mileage I've maintained for a good while has been 45-50.