Training on a Friday?

Usually Friday is a day off but with things being mixed up this week and not being at work I thought I may as well go running. I decided it might as we be a worthwhile run so I ran the 10 mile circuit at an easy pace. I had in mind that it would take 65 minutes but with a mild headwind my time at halfway was 33:30. I was mindful of keeping the effort the same all the way home but think I may have gone a bit too easy at times. It would have been easy to run progressively harder and acheive 65 mins but that wasn't my idea for this run. In the end, 66:16 was quite acceptable. On my final Sunday run prior to a marathon I always run this exact 10 mile circuit at an easy conversational pace. It gives me an indication of my fitness and can be compared to previous years.