Been working hard on my Aliner over the last year.
Replaced the radio, repaired the cassette potty door lock, screwed down the microwave that was sliding around loose in the curves, replaced the

refrigerator, and NOW getting around to replacing the memory foam mattress. More on that last point .....
Our Aliner has a design with a sofa in the back that slides/converts down into a bed. Which is the way we keep it given how much use it gets from the two of us. Travelling solo, I have slept on the sofa in the sofa config which is not a bad sleep when use need a sitting config during the day (rain, cold, etc.). But that has been rare.
The sofa cushions (seat, back) provided about 2 inches of loft and a cheap memory foam topper another 2 inches. It was just an "okay" arrangement. Not great sleep but okay sleep.
I learned many years ago from backpacking and camping with the Boy Scouts not to skimp on the sleep mattress. It's sort of like climbing Everest: you die a little bit every time you sleep above a certain altitude. All those nights over 10,000 ft elevation kept me moving up to the next plush camping mattress. So for the Aliner, selecting a new mattress (memory foam) meant moving up to a better solution.
The cushions in the back of the sofa are fabric/cloth and held up okay but the seat cushion was covered in some sort of vinyl fabric and was starting to flake off when it wrinkled/crinkled/laid on (7 yrs old). So I plan to pull the sofa cushions out of the trailer and put in a full-time memory foam mattress. Chose a 4 inch ventilated cool gel memory foam off
Amazon. Opened it up tonight to let it "breathe" and "inflate" before I move it into the Aliner this weekend.
It's slowly expanding.
It's a pseudo-Queen size (60" x 80") so I will swap out the old sofa cushions and install this over this weekend in preparation for our trip to the Fort in January.
Looking forward to a better night's sleep.
Ed
PS - the instructions say the memory foam has to sit for about 24 hours to inflate and air out any foam smell. Haven't noticed any smell so far ......