I don't always workout twice a day, but as my first workout was only 15 minutes and I am more of a runner than a weight training kind of guy, I wanted to do a run in the evening.
My first run on my treadmill in a few weeks went well. I am not too fond of the treadmill, but it is an absolutely necessary part of my routine as I just don't have time to run usually until night time.
The run was a 7 MPH setting at 3% incline for 45 minutes. I went about 5.6 miles.