That's one of the reasons I started using clear cartomizers like the Diamond carto from GotVapes - so I could see inside the carto and always know if the juice was getting icky. Then discovered CE2's and fell in vape love. To me the CE2 type or versions based on the same technology is the best of all vaping worlds.
Hits like a 306 dripping atty (tons of flavor and vapor), you can see the juice always through clear tube, no filler material to absorb and thus waste some of your juice, no airy hits from filler material, no poly fill to burn, juice goes right to the coil, coil does get caramelized sugars on it but it's easy to burn off the coil and reuse like new.
If your still using regular cartos and you haven't tried a CE2 type yet, I encourage you to try one.