You should NEVER smell fuel in the cockpit at any time.   If you do, this should be an immediate red flag and indicates a fuel leak.  Every time I open the door on an airplane, I smell for fuel.  I cannot count the number of times I've mentioned a fuel smell to the owner when I was to give flight instruction and the answer was always.  "yes, it smells like that if the plane has been shut up for a while-that's normal".   This is not normal and even though it may be a small leak, it is a leak and that is dangerous on several levels.  Just because that's the way it's always been doesn't mean its ok.  

RonG