Well, just from experience I would have to differ with what she said. All of the tarts I poured (a long time ago before I started reading this forum) that were put into polyethelene bags and portion cups had virtually NO scent left to them three months later. In fact, the FO had begun eating through the bottoms of the portion cups. I thought it was the wax and gave up on it, but have since found that using polypropolene absolutely does make a difference. I have some now that have been in bags and cups for six months that actually smell even stronger and no FO eating through the cups.