my dad always drilled it onto my head when i was a young driver, to always fill up at a half tank, esp in the winter. " that way you'll never run out, just in case you get stranded some where"
he was a scout, and took the "be prepared" to heart.
to this day, he keeps at least a month's supply of food on hand. and at least a 3 day supply of water, in case the power goes out, and we can't pump from the well.
that being said, on a summer road trip I'll run until the light comes on. dad fills at a 1/4 on the same trip.