The issue of tanks full or empty will always err on the side of fill them up, however if you leave a plane in humid conditions for a period of a month or more the condenstion becomes more significant.
Now for the MOGAS users and in Europe this is more common than here in OZ, the bigger problem is Premium ULP is enhanced with octane boosting products like Benzene, which easily evapourates, before you know it, you are back to regular ULP, so fresh is best with PULP.
Just a thought....
J
