Should a down mat be stored unrolled same as a sleeping bag?

I leave my synmat just loosely folded in half with the valves open, I either read that somewhere on their site or stu told me to

Exped info is here http://www.exped.com/en/mats-care-and-storage
Store your mat unrolled and with open valves in a dry, cool and dark place such as under your bed or the attic.Keep away from pets!
... and if you live in a mouse infested crumbly old hovel keep it away from mice who just love to chew expensive kit.

Thanks guys, thought that might be the case.