In my case, there will likely only ne 18" or so between the lights and the track.

Ken, try this simple test. Place colored file folders, 1/2 covered - 1/2 exposed, under a florescent lamp at 18". Leave the lamp on for 6 months. Examine the folders. I suspect you will find the red, purple, and yellow folders quite faded with the blue and green folders slightly faded. Since pigmentation used in office paper goods has less UV durability than pigmentation commonly used in craft paints the folders will give you a rough idea of worst case fading. While you are at it place a few Woodland Scenics items under the lamp also with control pieces stored elsewhere.

You would also need to put samples in the same area but not under the light... a control group.  Office products like that fade over time anyway... and so does WS products.

Steve