When it comes time to refuel do you stick a tenner (or other arbitrary amount) in or do you fill the tank? How often do you find yourself refuelling? How far does a full tank get you?

I wait for it to start bleeping at me and then go and fill it to the brim, about £45 and that will last a month easily (assuming no major road trips). Full tank will do me about 380-400 before the fuel gauge starts flashing, once carried on til about 440 before actually stopping as I refused to pay motorway services prices. Was probably on fumes by the time I eventually stopped.