In reply to mastermiaow:
Well assuming that your sleeping mat hadn't deflated, and you weren't ill, or undernourished, I'd guess that you've lost some down, or lost some loft from the down you've got. Either way, I'd email Rab and ask if they could take a look, and refill it and/or wash it for you. Last time I checked they had washing machines on site, plus they can either add extra down, or totally replace the down with new. If it's been stored well for 10 years, maybe just a top up would suffice, but if it's been stored compressed then replace the down for new bouncy lofty down.
IMO