So I have a heap of G1 figures in individual Ziploc baggies, packed carefully with their accessories and instruction booklets, in an opaque storage tub in my basement, near the dehumidifier. I always assumed that sunlight/UV was the prime cause of yellowing but...I'm not so sure anymore. I don't know if I'm going crazy or what but I swear some of them have just started turning yellow in the past couple of years! For example, I opened a baggie-fresh Omnibot Downshift back in 2005 or so, barely handled it, etc. I just pulled it out of the storage tub and it has a touch of tan to the once beautiful white plastic. Would this thing really go 20 years in perfect white condition and start to change all at once? Are there any proven storage conditions for keeping TFs as non-yellowed as possible?