There are just too many variables including how you fly.
Most people do not fly at full throttle the entire flight. I seldom am at full throttle.
That said, most people that I know have had enough of flying for any one flight and land long before the tank is empty.
My average flight still leaves me about 1/2 tank when I land.
There are allways exceptions to the rule, I have seen combat planes run out of fuel halfway through the heat when the starter delayed the start too long.(they have small tanks to begin with)