Like I said, I take an hour over a rebuild every time I change the cotton. I take the whole tank apart except for the coils, then clean the deck and the coils as thoroughly as I can. I also make the cotton a fraction looser through the coils to allow for the fact that the cotton expands so that I allow as much juice as possible to flow to the centre of the coils. I also keep the wattage down to a level where I avoid making the cotton become burnt too quickly. Finally, I've got into the habit of releasing the fire button a second or so before I stop inhaling to allow the airflow to help the coils cool down so juice doesn't cook on the coils and gunk them up too quickly. The cotton in my tanks right now has been in for 2 or 3 weeks and the taste is still excellent.