We're now 2 months in, and the strips of colour have spent all that time in a south facing window.
We've had a bright and sunny late Summer and early Autumn (Fall, for our trans pond chums) and I've exposed the next section of the test sheet to reveal... ABSOLUTELY NO FADING WHATSOEVER in either the Winsor & Newton or the Dr. Martens Hydrus colours.
I did't think it was worth posting an image at this stage. I'll post an image at the end of the test.
Based on the results so far, I've decided to use the Hydrus colours on my next woodblock print, which I've finished cutting and have just started to print. I'll post that in the next few days.
Here's my post at the start of the test: HYDRUS TEST START.