Now that I have the Biowin and Nyletherm in place I no longer will be using my oil boiler for heat or DHW but I understand that I should exercise it from time to time. I have a little less than a quarter of a 250 gallon tank's worth of oil. I haven't turned it on for a few months but I was thinking of turning it on once every other month or so to let it run for awhile. Also, how long can heating oil sit in a tank without going bad? Any recommendations on maintaining an idle oil boiler?