My setup, liquid, settings, etc. never change (see below). I find it's worth the trouble to rewick about twice a week and rebuild about twice a month. The part of the wick under the coil being replaced is only a little bit darkened but replacing it improves the
vape, I don't know why. The wire I'm replacing every couple weeks is a black color but there is no build up of anything. I don't know why the fresh wire matters but
throat hit improves noticably. I don't notice that rewicking or rebuilding changes flavor much but I use very little flavoring in my DIY.