SEMS told me to not use the gas cylinder to inflate the rafts because the gas comes out very cold and makes the rubber brittle. They test inflate using room temperature air.
No idea if there is substance in this but that's what they told me.
I can't imagine. A couple of weeks ago we had our annual sea survival training (in the swimming pool) and inflated some expired lifevests and a dinghy (from the 1980s, more than 15 years over it's expiry date!). Everyting worked perfectly and I saw the dinghy this morning in the corner of the hangar still fully inflated. It's more difficult to get the air out of it again than to inflate it. Obviously, the rubber is 100% compatible with cold CO2 gas.