Of course they told you that - the phone monkeys are probably told to say no to anything other than sticking stuff in the bag for storage. Because if your husband dies of cancer, and he went backpacking all the time and used plastic bags this way, and you decided with no real basis for it that the plastic bags caused his cancer, and the company phone monkey said "sure you can use them that way" - guess how many lawyers and so forth the manufacturer would end up paying for? Doesn't matter any more whether you are actually at fault. I carry ten million dollars in coverage in liability insurance, not just to protect me in the event that I do something wrong in the course of my working in my chosen field, but to protect me from the more likely occurance of having atrocious legal fees in the event someone else thinks I have done something wrong, and I have to fight for my reputation.