I disliked cotton just cause I was rewicking every few days from the cotton getting plugged up or burning so with 2 of us vaping it became tedious. I used Hemp fiber in my protank builds for eons, a little bit of prep to remove the off colored shards and bunnies but hemp kicked the chit out of cotton in lifespan. I've been using rayon now for well over 2 years in my kayfuns and now subtank builds. Once you get the tail thinning down rayon is superior in so many ways to cotton.
With cotton the juice flows inside the fiber thus it expands so after vaping the cotton fibers begin to clog so your loosing fibers one at a time until the dryhit then burn cause all the fibers are plugged up, so your using a heavy sweet juice the fibers plug up faster.
Rayon the juice flows outside the fiber so it has to be packed tight in the coil then settles some and doesn't shrink like most believe but you have to thin the huge mass tail cause too much tail bulk and you choke the rayon. There is no clogging of the fiber like cotton so the rayon lasts as long as the coil performs unless you burn from too hot. My coil cocoons with YUK long before the rayon poops out and thats 150+mls DIY juice. Rinse the rayon and its barely browned looking like it can be used again vs the cotton that turns black from burning juice. Everything about using rayon is opposite to how you use cotton in a build.