Disappointed after several months

Had high expectations for this mattress based upon so many positive reviews. I've recently gone back and re-read some of the reviews, and did notice that many were written after just a few weeks of using the bed, which probably is not the best gauge to go by when trying to find out if other people are happy with what they bought. Our first few weeks on the bed were good too. We do have the proper foundation recommended yet this bed began sagging on both our sleeping sides of the bed after just a few months. Have woken many times with a numb arm and hand. Has not provided easing of morning backache as I had hoped for. The edge support is lacking. During the last summer we slept way too warm on this mattress. Now in winter it is not sleeping hot which is a relief. Our mattress is medium, yet it feels too firm overall, even with the continual sagging. Reading over the warranty on Nest's website, I find that the sag has to be an inch or more to get warranty service. Ours sags not quite an inch, but even a little less than an inch is quite a bit of sag, especially for a new mattress. We actually have a permanent hump down the middle of the bed. Have used the bed about 10 months now, and will be switching it out with our guest bedroom mattress and foundation. Our guests can sleep on this uncomfortable mattress until we replace it with something else😀 I was going to buy a mattress topper, but why spend the extra $ just to disguise what is for us an uncomfortable bed?