Hey Jason. When I honestly first started with watercolors, I was worried about my paintings fading quickly because the colors seemed to lose their vibrancy after a few weeks. I had a basic set and didn't want to splurge on new ones right away & so I experimented with different techniques to make them last longer. I tried mixing the paints more thoroughly and applying thinner layers and but that didn't make much difference.
What really helped was switching to higher quality paper that absorbed the paint better and prevented it from breaking down over time. I already had some archival paper lying around from an old sketchbook, and using that instead of cheap stuff made the colors hold up much better without any fading. It turned out the paper was key to preserving the pigments.
I also started framing my finished pieces under glass and keeping them out of direct sunlight, which solved the issue completely. Now my early paintings still look as bright as when I made them, all without buying anything new.
Totally agree that paper and keeping pieces out of sun make a big difference but it also starts with choosing lightfast pigments. Look for artist-grade paints with ASTM I or II ratings and favor staples like ultramarine (PB29), phthalo blue (PB15:3), quinacridones (PV19/PR122), nickel azo or Hansa yellow (PY150/PY97), and earths like burnt sienna (PBr7), while avoiding fugitive colors like Opera Pink and genuine alizarin crimson. A small primary set from an artist line using those pigments will stay bright for years even before framing.