Hi oceanmd,
I think the first place I would start in any search for a new mattress is post #1 here and the information it links to. This will help you know what to avoid and what to focus on both in terms of mattresses and the retailers or manufacturers that sell them.
OMF as you know is a factory direct manufacturer and they do use higher quality materials than mainstream manufacturers in all their budget ranges but sometimes the problem with sagging is just polyfoam layers that are too thick and soft even though they are better quality/density (they use1.8 lb polyfoam which is higher quality than most mainstream manufacturers use). You can see more about this in post #326 and #329 here (and some of the other posts they link to)
The quality of the foam, the thickness, softness, design and suitability of the layers and the mattress, and the body type and sleeping positions of the person all will have an effect on how long a mattress will last for a particular person. It’s never the manufacturer or the name on a label that is the cause of sagging … it’s always the materials and design which you could find in any similar mattresses (and many of them including the major manufacturers use use lower quality materials yet which means that these issues can happen even faster).
Once you’ve gathered some basic information about mattresses and the materials inside them (and in a couple of hours you will know more than most people who sell mattresses :)0 … then the next step is to “connect” with the better manufacturers and retailers in your area and I would include OMF as being one of these in any area they had a store. Of course it’s still important to make sure that you choose wisely and know the details of every layer and component in a mattress you are considering so you can identify any potential weak links in the mattress and make meaningful quality and value comparisons with other mattresses.
If you let me know your city or zip I’d be happy to let you know of any other options or possibilities in your area.
Phoenix