It's funny how different folks can have opposite experiences. I've done like XJet and for over 40 yrs. I've emptied my left over/overflow back into my main fuel jug. You can count the number of dead sticks I've had in the last ten years on your fingers so it's something more complicated than just the residual fuel causing the problems. I've been flying heli's for over 5 yrs and the only dead stick I've ever had was a glow plug that had NO element left when I got it down. (Yep, that run got pretty lean due to the muff pressure line splitting in flight) I defuel/catch the overflow right back into the main jug on the heli's as well. I can't explain why some have more problems than others with this method but the answer isn't as simple as it might seem as I live in HIGH humidity Houston, TX of all places and have for all 52 yrs of my life. I've flown glow powered planes since I was 6 (my uncle flew control line and got me started). I was very poor growing up and the catching the spillage and pumping the leftovers back into jug (back then it was all cans) was a way to not waste anything. One thing I will venture a "guess" to is it may have to do with how long the fuel sits AFTER it gets moisture in it because once I open a jug it don't hang around long (couple of weeks tops).