Stored kerosene can go bad. When kerosene is being stored, condensation can seep into the container and cause a problem. Sludge can develop from the mold and bacteria within the kerosene, and that causes it to break down.
Be sure to store kerosene properly to keep it from going bad, and pour kerosene that won't be used for a while from the lamp or heater into a safe container. It is important to place the liquid in a sealed, opaque plastic container specifically designed to hold kerosene. This is both for safety precautions and to preserve fuel.