Probably more careers are cut short because of not getting enough sleep while training hard. Everyone requires a different amount of sleep, but everyone will always need more sleep when training hard. If you are going to increase your mileage, while at the same time getting less sleep, you are asking for trouble. One of the biggest reasons so many people improve a lot out of college is because they start getting more sleep as they increase their training(that is if they are at least a semi-professional runner and not having to work 50-60 hours a week).
I guarantee you that many people will respond that sleep is over rated, you only need 6 hours of sleep, more mileage is more important than sleep, etc., but it is pure physiology. Your body requires a certain amount of sleep and hard training makes your body require even more to recover properly.
Is there anyway you can add the mileage during your lunch hour? Also, you can always add more mileage on the weekends when you can get more sleep. There are ways of increasing the miles without losing sleep.