So I'm starting to make my own lotion, and I was confused on which sort of bottle is going to be best for this process. I can't find wether HDPE (http://www.specialtybottle.com/index.asp?PageAction=Custom&ID=24) or PET (http://www.specialtybottle.com/index.asp?PageAction=Custom&ID=21) is going to be better for long term storage. Any advice?