Do you listen to music or do you play pink-noise to burn them in?
I used to play different Genres on shuffle at low-mid volumes for about 4hrs at a time then let them rest for about 2hrs and repeat up to about 40hrs. Lately though, when I receive a new pair of HP's I've been listening to them through the burn-in period so I can hear the changes they are going through which is pretty exciting/enjoyable.