I fill at 1/2. Particularly in winter. And I keep a few NATO jerry cans (which is a racist term but with us Germans it's allowed

). I detest running low on fuel. Keep the car and tractor going.
Also keep track that I have the fuel on hand to get to the cabin, our BOL if something should go south here. You never know if a train derailment and chemical leak could force you out of your house.
I miss having an actual gas "tank" when we had the farm. We had a 200 gallon barrel and man is it nice for gassing up the equipment or filling the farm pickup. Real nice to spend a day at work and not have to think about running to the gas station that's 20 minute's drive. I guess the farm mentality stuck in me.
It is mind blowing how many people don't have enough fuel in their car to get to the hospital. Real dumb.