I have just started to "roll to air" on every third stroke....prior to this, every time I would roll to the left...air was taken on board. All of a sudden I can now "sense" the feeling of swimming downhill and there is a definite sense of increase to speed. I had not ever considered exhaling in a controlled way though....I would usually exhale quickly, under water.
After reading these posts in seems I may have been causing a leg sink (increasing drag) by doing so. Very anxious to get in the pool now and try out this new (for me) practice.
Even with all the imperfections of my technique, though, I find that I am swimming better than I ever have. Even to the point of people coming up to me at the pool and saying "you obviously know what you are doing" A 1000 meter swim is just not daunting to me.....on to 1500m.