Since I replaced the old mattresses, three years ago, my boat came with I have had so many people state how comfortable my beds from mattressnextday are. Some people go so far as to call it the best sleep they have had.
My old mattresses were standard 3 inch thick, vinyl covered mats that were well past their prime.
I could have gone with $2500 custom made mattresses from Mattress Knoxville manufacturers, but I found a different, and MUCH cheaper, option.
I got six inch thick, medium density, latex foam from the Foam Factory. I ordered the queen size for $577 and then had them cut it for another $100. They did such an amazing job with the custom cutting that each mattresses fits perfect in the cabin and the guest don’t even know they are cut in half (this allows me to get to hold under the mattresses). Plus they will ship free anywhere in the US. I also decided to get the best bed bug mattress encasement, just in case I ever need it.
So for less than a third of the price I got a just as good of a mattress as the fancy manufacturers and so far I have had mine for 5 years (I replaced my bed first to see if I liked it) and have not seen the foam breaking down at all or getting crushed in the middle.
If you need a new bed you would do very well talking to the Foam Factory and trying their product.