S N A K E O I L !
That's my general opinion on the mattress industry.
Our boat came with quite firm foam (non-memory) upholstered mattresses. From the very beginning, I had always presumed we would find something better and replace them. That has turned out to not be necessary, fortunately, as we find we sleep quite well on them. Since we like a cool sleeping area, we have a heated mattress pad under the regular mattress pad. For cool nights, we simply turn on the mattress pad 20 minutes before retiring in order to pre-heat the mattress. Yes - the mattress pad runs on AC, but they are very low wattage and barely put a noticeable load on the inverter.
Since you are in the PNW, a heated mattress pad might be a nice touch for you.
If you go the "memory foam" route for your mattress, I have a comment. We have in our home a Tempur memory-foam mattress that's still going strong after 18 years. We like it a LOT...with one exception - it can get seemingly rock-hard if you keep your bedroom at, perhaps 60-63 degrees during the cool seasons. In this case, you climb into the bed and await for the "slab" of a mattress to warm up a bit with your body heat (about 15 mins). Then it becomes more flexible. To address this, we use a heated mattress pad connected to a timer so the mattress goes on "pre-heat" automatically every night. The timer then shuts the mattress off after we've been in bed for 1-2 hours, as it can be unpleasant sleeping all night with it on (dry mouth, too warm, headache (magnetic field??)).
One can buy hand-made horse-hair beds here in Sweden, if one is prepared to take out a mortgage for a $50k mattress & spring set. Yikes! Snake Oil on steroids!