I have not been sailing very long but have been involved with diesel fuel in
the busing business for quoite some time, fuel has bacteria in it that is
always growing. you can prolong its life for awhile with addatives but in
time it will get slimely and clog your filters and not be nice to injectors.
it is best to keep tanks full in cold weather or changing temps to help stop
condensation. yes it best to keep using up your fuel and stop stuff from
growing in your tank. one year is a long time for d. fuel.