The message is a small volume of gasoline has a larger temperature variance than a large tank and will reach higher temperatures on a hot day. If someone wants to store gas it should be in an underground tank which is regulated by the EPA with substantial fines if a leak is found. EPA says there are no underground burying of tank restrictions for agriculture use. A local distributor says gasoline expands more than diesel. He also said to be sure to keep drum covered so rain can not enter gas by collecting on top and use a stabilizer available from a diesel engine supplier, Boater's world or the more expensive version from a motorcycle dealer.
Stabilizers reduce oxidation and contain a biocide.
The stabilizer should be added immediately when fuel is purchased. I was told one can smell when gas has been affected by oxygen and goes bad. It was only described as unusual non-gasoline smell. Others have said it smells like varnish. The USDA says the bad gas can have a sulfur smell and looks dull.