Kerosene will last years which is kind of cool. Minimally three years.
In theory the kerosene (just like diesel) could wick enough moisture over time, and then a fungus could start growing, which in turn could clog up like a wick type heater...
If you want some piece of mind, just add some biocide made for diesel or aviation fuel...
I use my torpedo heater very infrequenty.
I bet the kerosene in it is 10 years old, but it fired up fine when i needed it a couple months ago.
