Does fluorescein decompose from long term exposure to light? I've had about one liter of fluorescein solution setting on the shelf for at least several years and one day noticed that it suddenly lost its characteristic green color. It's now a light yellowish-green solution that seems to have lost the property of fluorescence altogether.

The container is a reagent bottle with a leak-proof cap so I doubt that the solution reacted with anything in the atmosphere other than maybe 100 mL of air that was in the bottle to begin with.

The bottle was exposed to direct and indirect sunlight on a daily basis.

Does it have to do with the decomposition of the fluorescein, and if so, what are the expected decomposition products?
Yes, Fluorescein decomposes due to exposure to light. 

See The Conservative Behavior of Fluorescein for quantitative data.