If you don’t use the sealer for a long time, you can save it like this. 
First tighten the lid of the sealer, then wrap the cap in a newspaper with a newspaper to basically block the air from entering the bottle. 
Put the wrapped sealer into the box and put it in a cool, dry place.
Remember to avoid direct sunlight. The next time you use it, just change the nozzle and it will be OK.
But pls don’t keep too long,2 months at most, or the quality will be affected.