For those who are concerned:
Even with conservation (special) glass, it is not wise to keep your art consistently exposed to brighter light, rather it be sunlight or interior lighting. If you do want to have your favorites on a main wall with consistent lighting, you'd do well to cycle out the pieces to prolong any fading.
The problem with fading is when you see the piece every day, you will never notice it until it's too late, as the fading occurs slowly even when exposed in a room full of sunlight. The day-by-day, week-to-week degradation is not easily discernible.
Conservation glass (from my understanding of what I've read), is a form of diffusion glass, which when side-by-side with normal (clear glass), you can definitely see the reduction in transparency. It doesn't take away from the beauty of your art, but that's because it doesn't stop light altogether (or it would be black), it just reduces/softens the level of exposure.
While it is wise to use conservation glass on any of your grails, it is best to keep any art you really care about out of bright lighting. I keep most of what I display in my basement, which is dry, and I've blocked almost all the natural sunlight. So, the only light on the art is when we're down there, and even then I cycle the pieces on my walls... But, I'd probably do this anyway just for the change!
I like to do my own matting and framing, so this is just a word to the wise passing on a little of what I've learned in the process.
My couple of centavos worth,
-Vaughn
PS: I'm always looking for simpler Wrightson pieces if anyone is interested in parting with any... I especially like prelims and concept pieces... I love grails too, but my appreciation is much deeper than my wallet!