For the past two days I've been experimenting with 30-second walking breaks every half mile during my one-hour runs. This morning I used them with my two-hour run. I felt fine during the run. I looked forward to the breaks and felt energized after they were over. I had pretty good energy during the run, and I ran the last half two minutes faster than the first half. I could have gone even faster, but I held back since this was a LSD run and not a speed run.
I don't really know if my energy today was from the breaks. All I know is that I felt great, better than I felt yesterday and the day before. Part of it is probably due to my cough being gone. I've had that cough for a couple of months, but it has been gone for a couple of weeks.