Boomer-
I can't seem to find any direct reference to a shelf life for Klean Heat, but others may be able to do so.
Considering that Home Depot and others store it over the summer and sell the same stock again the following winter, it must have a shelf life of 12 +12 months or so, probably longer.
It would logically have a longer shelf life than basic distilled kerosene because of its very low concentration of aromatics and sulfur. Since it's obviously been purified several times, it's probably much more uniform in the range or types of hydrocarbon molecules present and more chemically stable, lacking the volatile odds and ends that can break down or recombine and produce "bad guy" molecues!
For an anology, we can look at gasoline. Automotive gas goes bad without additives in a period of several months to a year, depending on who you want to believe and what standards are applied. "White gas", such as that used in Coleman lanterns, is said to be indefinitely stable and have no shelf life for all practical purposes. It too, is a more uniform, more highly refined product.
Maybe some petrochemical engineer or someone else more knowledgeable can correct me if I'm wrong on any of this!
Joe. :teeth