Working at auto parts stores for many years untill recently, the only real downfall is this, you will always get particles in your gas (hence the need for a fuel filter) however the fuel filter doesnt have a bypass valve like an oil filter so when its cloged it doesnt allow fuel to pass... those particles will settle at the bottom of the tank, especially the lower the fuel in the car, so when you let the gas get to low the pump will pick up particles and it will clog your fuel filter faster. Now dont get me wrong, there are alot of other conditions to this happening such as the age of the car, quatlity of place you get gas,etc... Also gasoline in small amounts can and will freeze, so its not always condensation causing the freezing. To make a long story even longer, its not going to kill you to let it run low, but it's not something Id always make a habit of IMO of course!!