This makes ramping up the running duration and intensity fairly easy. Since I am only dealing with minutes, I can do 35 minutes on my easy days and 45-50 minutes on the harder days. Those harder days include intervals, hills, and anything else I can think of to make things interesting.
Best of all, I get a good workout and can stretch, shower, and walk back down the hall in about an hour. It is a nice way keep active during my busy schedule at home and work.