Lower ohm might help, it'll be a little hotter and might keep it from gunking up so fast. My first guess would be the juice. They don't seem to like some juices. Darker or sweet ones especially.
My favorite juice Wyatt Earp starts gunking up about 1/2 through the first fill and by the end of the fill it's like sucking a golf ball through a garden hose. I cleaned it, tried the same juice again, same result. Started off great and by the end of the fill was completely clogged.
I cleaned it again and tried a lighter colored juice, Mimosa and I'm on the 3rd fill since the last cleaning with no drop in performance.
Also....if you're putting the washer back in...the one that goes above the filler seal, you might try leaving that out. For some reason I've found it clogs a little faster with that in. Might be condensation collecting on it. It really serves on purpose anyway if the filler ring is not taken out.