I would be hesitant to buy wholesale into the plastic bag idea given that humidity control is allegedly a major factor.
Originally for resin balls we thought heat was the primary driver, but before we knew better a lot of us carried balls in the car all the time so we could just drop in and bowl, and while that would lead to a lot of "sweating out" of oil or plasticizers, we didn't see a ton of cracking in the early days. Of course, in the early days of resin, covers were much thicker, which may have had an effect.
I fully believe the pressure point theory and try to physically rotate my stuff on their racks from time to time, but I have kept all my equipment in a temperature-controlled area now for probably 20 years. During that time, I've moved a bunch, and the times I've had the most problems with cracking were the times in which I lived somewhere with humidity conditions I couldn't control well (i.e., closed-in garage with a split-system AC that kept a stable temperature, but had trouble properly dehumidifying due to the status of the insulation in the room).
Keeping a ball inside a plastic bag, therefore, makes me wonder if you'd trap moisture in the bag, and if so, what long-term effect that would have.
The other thing I've noticed over the years -- I've got 70+ balls in my home shop right now and have probably gone through another 30 that I no longer have -- is that I have had the most cracking problems from balls poured in the old San Antonio plant that was Columbia, then 900G, etc., and it was by a degree large enough to be statistically significant to me. And I say that as a big fan of 900 Global stuff; if I had to make an arsenal right now from one company, it would be 900G/AMF, all of it. I realize I'm just one data point, but that's been my experience.
Jess