Hmm, thanks for those photos target-misser. I've checked the manual (mines a Crossman branded, so relatively recently made, and looking at the impressed writing on yours I guess it is to) and nothing is mentioned about not storing with the CO2 in. I just do as the manual suggest, and put a small blob of suitable oil (I use the one for Brocock BACS) on the end of the cartridge before fitting it. I probably only need to change it every month or so, but haven't noticed the seals degrade so far. Thanks for the update also Ian.