I did a some lightfast testing about a year ago and at that time I had bought portrait sets of Koh I Noor colored pencils and watercolor pencils. I put the color swatches in a south faced window with one part covered. It has been sitting there for about a year and four months today when I took it down. I have put it in an archival display folder. Will update this post later with results and conclusions but for now I just write this so that I won’t forget about the date.