I've heard many accounts over the year of old G1 era toys being stored in a dark space, away from the weather, or even significant temperature change being brought out and having yellowed or otherwise damaged plastic. UV light probably does have an accelerating effect but complete light isolation isn't the answer. And in my mind, I'd rather enjoy having the toys around than never seeing them because I'm scared of them potentially damaging even though the process of never seeing them would not necessarily avoid the damage.