Go the younger option:
Plastic parts shrink over time (even in an controlled environment) - this as well as the chemical changes that James pointed out earlier, will ensure that the plastic will stress and crack over time.
By the time you can see stress cracks with the naked eye - it's all over by then!
Plastic products do not live forever as greenpeace would have you believe, UV light, humidity and heat are all catalysts - and cause the structure of the plastic to change at a molecular level... (This is important because the molecules have to be in "alignment" to give plastic it's strength and clarity/transparentness)
I'm not a salesman for RTBB/PBL either...
