Weigh the canister. If the bottle weighs in correctly (printed on side) leave the raft inflated for 3 or 4 days then suck the air out with a vacuum. Then, on a sunny warm day fold it back up. Take plenty of photos while you're unpacking it. Don't put all the extra junk in it except for the liferaft stuff (paddle, repair kit, new flares, etc.) everything else (water, food) in a ditch bag.

I was going to throw mine in the water and pull the cord but if you empty the bottle it's almost impossible to get someone to refill it.