When you are packing for long-term storage you need to make sure that you complete the process carefully so that your items make it to the end of the storage term without being damaged.
First of all you need to avoid plastic bags for packaging wherever possible. You might think that plastic has more protective qualities than other forms of packaging; however, if anything is even slightly damp then the plastic is only going to make it worse and speed up the development of mold.
For long-term storage, the stronger the boxes the better. Boxes of equal size are easier to stack and will help to maximize the space within the storage area. Your moving company storage facilities will vary depending upon the company; for example, some use racks and pallet storage.
You need to make sure that you do as much as you can to protect the more fragile items in your storage area; your moving company will be able to offer you advice on this. Make sure that boxes of fragile items are clearly marked so that nothing is accidentally stacked on top of them.
Opt for vacuum-sealed bags for fabrics wherever possible. Not only does this help you to make the most of the space but also this can really protect your fabrics from damage. The vacuum-sealed bags are a small investment but you will find them useful for storage in your new home, as they can be used again and again.