Bests & Worsts Reviews from Amazon

Just now reaching 6 months of ownership - which I believe is a fair amount of time to give a product before writing a review. Initially - Pretty solid mattress, arrived on time, expanded to the 11" as stated, pretty comfy for a Sub 300 dollar mattress... 4.5ish months in until this morning - HUGE sinkage in the middle of the mattress, not even sure if that is how to properly describe it, but its as if the foam/gel/whatever is like broken which creates a massive sinkhole...which has progressively gotten worse, leading me to have to sleep very close to the edges vs the middle - and now both edges where I rest my head on each side are sinking as well... I am a 6ft, 200lb male - so, its not like I have some massive weight on this thing - and it is setup on very solid, real wood, platform bed which provides a great deal of stability... I have sent Amazon an email - still waiting on the response, but...at this point, the mattress is basically useless as I can't sleep anywhere on it anymore... Update - Amazon customer service is one of the best - they are working with me on finding a solution that works with "my schedule" - thus, Mattress still gets the 1 star, but Amazon gets 5 stars