I know I'm fighting a losing battle color wise I will preserve the color as long as possible but it will fade.

The shallac is to seal and start the protective finish and protect from the finish varnish. The epfings is the best UV protection on the market so my research shows.

I have a shave brush with just UV varnish that has help up pretty good for a couple years.

How do I know when it's time to move to the next grit?