Storing a Waterbed Mattress long term
To store your mattress long term requires you empty it completely and then add several large bottles of conditioner and ensure the conditioner gets circulated. This protects the insides.
Warning: Fiberfilled mattresses should be drained down so they look wrinkly like a raisin. If they are not dry enough, the fiber will slide and slip inside when you roll it. If the fiber stays out of position inside the mattress for a while, the tethers will not be able to pull the fiber back into position.
Then you need to wipe down the outside liberally with cleaner protectant to protect the outside.
The mattress should be rolled from bottom to top. Get two wardrobe boxes and connect the two boxes so they are long enough to the cover the rolled mattress. Slide the mattress into the box and store in a climate controlled area. This does not mean the local storage place's garage or your freezing cellar or attic. Extremes in temperature and humidity will harm your mattress.
You need to take the mattress out each year and add a bottle of conditioner and wipe down the outside liberally with cleaner protectant again. This will help keep it from cracking or drying out.
See Moving Mattress for more complete directions
Be sure to use an electric pump for fiberfilled mattress and if it does not remove enough water, use the wet-dry vac method to get the last of the water out.