But to me some reason cotton tastes...twangy? Not sure how to describe it really but it definitely changes the taste of my juice compared to silica for sure. I'm willing to give wick time to break in but imo if it doesn't taste better after about 2 mils I'm done with it. And cotton never seems to improve for me. I've tried two different brands of organic cotton and I get the same taste from both.
Did you boil it first? If not, It might have had impurities from processing.
Not all cottons are equal, I've used several different kinds and brands of cotton (balls, yarn, square braided candle wick, cheescloth, etc) and found their performance to differ widely. I use Sugar n' cream brand 100% cotton yarn #4 white, boiled it twice in distilled water and air dried.
I don't find much of a break-in time if at all, just make sure your wicks are well saturated and given time to fully absorb the juice before vaping.
It may indeed be a personal issue where you pick up on things that I don't and vice versa, but this is just what I've found from trying a lot of wicking materials.