It is ideal to train twice per day instead of once per day, you can train at a much higher volume. In other words, there is more benefit to running 10 miles in the morning and four in the evening than only 10 miles in the morning. In the past my primary workout has always been in the afternoon, after work and before supper. Here's the thing, when I do my main workout for the day in the morning before work, what am I supposed to do after work? I haven't had cable or Internet for five years. I fill my time running, exercising, and cooking. Yes of course I watch movies on DVDs and spend time on the Internet on my phone, but not 5 pm to 9 pm every night.
After getting home from work, I get a little bored, and go run, or more commonly because of the temperature, bicycle. So my volume is increasing quickly, this is a good thing.