It cant go bad as it is a compound (propane usually) which needs to have a chemical reaction in order to change its properties. In saying this the tank could be "bad" in which case the gas could have escaped and has emptied the tank. Once the gas has all leaked out to equalise the pressure from outside to inside the tank the gas could then mix with normal air and eventually mix so much that there is basically only normal air left.

The white gas I am familiar is a a very light hydrocarbon that is a liquid at atmospheric pressure. Kind of like lighter fluid. It won't go bad if kept in an air tight container in a cool place.

It will go bad as the lighter smaller volatiles will deplete more quickly through diffusion
unless the container is absolutely airtight