Not sure it was ever used as I bought this for my girlfriend, but we never went wild camping, which was the intention. Hence listing this as new (other).
Its been stored according to the manufacturers instructions... that is, unrolled, flat... and with the valves open, so no danger of mould building up inside the foam structure. In other words, it should be pristine.
Further technical stuff can be found on this page...
https://www.rei.com/product/719786/therm-a-rest-prolite-4-sleeping-pad-womens-regular