Bests & Worsts Reviews from Amazon

This is my 5th Zinus memory foam mattress purchase. The first three were purchased from Walmart and were fantastic. They were the 12" mattress and expanded as they should. The 4th one I purchased from Amazon and it was also a 12" mattress. Unfortunately that one never expanded like it should and the corners look horrible. I just let it go though and lived with it since it was in guest bedroom. Just ordered an 8" mattress from Amazon and it isn't expanding either. Right now it's at about 5 1/2" and the corners arent expanding at all or barely. I'm going to give it a couple of weeks and if it doesn't get any better it's going back. I'm starting to wonder if there's a shelf life on these mattresses and Amazon is having issues with their's because they've been stored in a warehouse for an extended amount of time. I'm sure the mattress isn't made to be sealed for too long before being opened up. I just know the Walmart mattresses did what they should and these Amazon ones are having issues. I will update my review in a couple of weeks. Update: Mattress never expanded as it should. I really think Zinus should sell their 8" as a 6", 10" as an 8" and the 12" as the 10" will all the problems these mattresses have expanded correctly. They all seem to fall a couple inches short of what they're supposed to be. With that said I returned the mattress and Amazon customer service was amazing. 5 Stars!!!!