I do 30/70 linen/leather, because it adds up to a nice satisfying 100. I'm leaning away from the 'warming up the steel' idea and thinking it's really just cleaning micro corrosion as far as the canvas goes. 70 leather is a good number for me; over that and I can start to get sloppy, as I tend to have my eyes wander to the mirror as I contemplate how it's possible for me to be getting more and more handsome as I get older. Some of you may not have this problem.
Carl