I haven't used ostrich in a year or more. Today I took her out for a breather and it seems the entire bag darkened in color. It could be that I haven't seen it in daylight for so long that I'm forgetting the. I faintly recall reading somewhere that ostrich darkens when kept in storage and lightens if it 'breaths' in the sun. Experts -- is this true? Should I let it sit next to the window??