Cels Forum

i don't know if you've seen it or not, but if you go craft/art stores (Michael's, etc), they have a spray that makes glass UV resistant.  Once you get the knack of applying it, it goes on fine...and only costs about $6 (just put tape over the frame or take the glass out of the frame before you do it, and make sure the glass is REALLY clean).  I've done about 20 frames off of one can so far. 
hope this helps :)
rosemary