What iv noticed with aged coils, is once the gunk starts building up on and around the coils, liquid starts dropping into the air flow and slowing start filling up the bottom base. Left long enough, start seaping out of the air flow holes or even through the 510 into the mod.
My thought would be that if theres gunk covering the coil and wick around it, the liquid isnt making proper efficient contact with the coil to vapourise properly, and so just warming the liquid making it more runny causing it to leak out of the fucked wick easier and drip into the air flow chamber...
Longer draws/higher wattage to compensate the lack of vape, maybe? = more juice used.
Im probably wrong, usually am, but spouting my nonsense usually causes someone with the correct answer to come along and correct me with the right answer to your theory.