nick I spent a little time googling on this topic and found nothing definitive but a couple of references. The best is below.There was also a couple of references to using a heatgun or iron to warm up the leather surface prior to conditioning to improve absorbtion (sp?)
http://forums.vwvortex.com/zerothread?id=1228253 - 3 It's recent so the author can probably be tracked down for followup.
summarized below:
by 2turbo4x4 leather experts....advise on improving older seats (pigbladder)_»
2:58 PM 3-15-2004
You can get wrinkles and creases out by doing this method:
Bucket with HOT water in it
Soak terry cloth towel or detail pad in HOT water and wring until damp
Use a leather conditioner (I use Lexol)
Spray a small area of the leather and use small circular motions with the terry cloth / detail pad.
When the warmth goes away in the cloth, resoak in HOT water and wring until barely damp. Continue with this method until crease / wrinkle is gone.
The idea is the warm up the leather a bit so that the pores will open up and soak in more conditioner.
You can also use a damp cloth and a heat gun, but you will need to practice a bit so you don't heat up the leather too much.
This method works very well for removing creases and strech spots.