I accidentally ran a 3.5 year long experiment.
https://lazygeckoblog.wordpress.com/2016/02/29/what-happens-to-pla-that-has-been-sitting-in-water-for-3-5-years-an-accidental-experiment/
Absolutely nothing? I would have expected the PLA to get wet at least… 
Was it in the sun or in the shadow? Cold or warm?
Ok you got me there. Yeah, it was wet. It was in a cool cupboard.
Ok. Cool. Still wondering what 3.5 years of sun would do. I’ve seen some PLAs go “white” after a few months of sun. But that’s just bad dye. Still no idea what sunlight (UV) will do over time.
My dreams of manufacturing a PLA submarine will now be moving forward.
I printed a swimming pool adapter in june 2012 (http://www.thingiverse.com/thing:25638). It withstood temperatures ranging from -15°C to +37° all year, regular heavy rains but most often harsh sunny says (about 300 a year, and probably 2-3 hours in the sun each day in summer). The layers eventually started to peel off, but the print was poor in the first place and well, it took about 3 years and I don’t think the sun killed it (chlorine neither… I would say mechanical stress during each careless usage).
I printed a replacement in PET, so I am curious to see if it will stand so long!
BTW the color was only slightly less saturated. I expected to post about it one day 
I have two single walled parts of pla outside since at least two years. One exposed to rain an sun hanging from a tree and one was burried partly into our composter. That was from the days AS every one used to copy the myth that pla is bio degradable. i don’t See any obvious defects so far. Will have a closer look in near future.
Was the jar sealed?
I’ve printed pool cleaner parts that has been fine. The water keeps it cool and solid. Outside the water in direct sun I printed a part that didn’t do all that well printed in black pla, I reprinted in white and it was fine for months.