The Metropolitan Museum's research indicates an extremely short life for autochromes on exhibition unless put in a low-oxygen environment during display. It's causing most institutions to determine that they should never procure or show autochromes, because they do not have that ability. But in my experience, autochromes have been relatively stable, especially when kept away from direct heat. I suspect it was their researcher Luisa Casella's method in creating "new" autochromes that caused this dye instability, since she didn't actually test historical autochromes themselves. Any one have any ideas on how stable or unstable actual historical autochromes are. I've yet to see fading in any and I've seen thousands.
Alex