Should we rotate kerosene heating oil from year-to-year?

you should be fine...what can happen is that the fuel whether it be gasoline or home heating fuel if stored for a long time can become less volatile due to the gassing off effect of evaporation and if burned can create a varnish that will clog very fine pores ie....carburetors. For you though, you should be fine. I would dilute the old fuel with new fuel on a 50/50 ratio so if you have 5 gallons of old kerosene just add five more to it by pouring into separate containers this will make your fuel more combustible and eliminate your problem. Don't throw it out though...offer it to any truck driver (they use it in the winter to lower the burning temperature), a church (they can add it to their #2 oil tanks and burn it), or a needy family that is burning home heating fuel bc they could use the help...that is if you decided that you don't want to burn it yourself

i would do it just to be safe. chemicals in oil can change over time and potentialy be deadly if lighted

If it were me ? I'd throw the old stuff out. Good Luck ! :)