I have a pair of ATH-M50's that I got around October of last year, and I noticed that the pleather has been very stiff. This was not a gradual development; I noticed maybe over the course of a couple weeks that the pleather had become much stiffer than it used to (around maybe november) and since then the pads have more ore less maintained their same level of stiffness. On both pads, the bottom half is much stiffer than the top parts for whatever reason. I ordered a new pair of pads a while back, and if the stiffness on the old ones get really bad I'm most likely going to replace them. My question is this: what are the ways that I can preserve the elasticity on the pads? I don't want to make the same mistake as before.