I've bought a new spring mattress for my 4 month old as the foam one he was using second hand from his big brother isn't looking as firm as I'd like and he's rolling to sleep face down now. I've read some things about airing new mattresses for up to six months (!) to allow outgassing of PVC, etc., but can't find any reputable sources about this and want to start using the new mattress ASAP. It's high quality and has no plasticky smell. Has anyone done extended airing?