My wife and I lived in this 40 ft single slide RV for 5 months over 2 summers.
We selected it for the quality of workmanship. Amish made maple cabinetry are still solid after 20 years and 50k miles on the road. Dual pane windows and day/night shades with window awnings allowed to front/rear low profile A/C units to keep the interior cool with minimal run time and noise.
The Spartan frame combined with the Cummins 325 Diesel engine provide a smooth Air Ride while easily climbing hills and descending them gracefully using the jake brake as needed. The Onan 7500 generator can run all appliances when running off-grid, which we often did when traveling the wide open roads. We upgraded the house batteries to 300 Lithium Ion batteries and 4 solar panels so that we could avoid running the generator unless we needed A/C or to do a load of laundry.
The 4068 floor plan allows full access to the entire interior so that the slide need not be extended for short overnight stops. The viewing angle of the HDTV is eye level when sitting in the leather couch (or recliner) which prevented neck strain. The fold out couch was used for several weeks and is very comfortable (I speak from experience).
Driving safety is enhanced by adding blind spot cameras and the improved color/night vision capability. We kept the stock b/w camera pointed at the hitch to improve backing. We towed our car by trailer and dolly many thousands of miles barely noticing it behind us. Our rig has a second box receiver that holds a bike rack so that we can easily use bikes even when hauling a car.
The basement is quite cavernous, holding not only the Norcold freezer, but also an inflatable kayak, solar oven, tools for the road and items we collected on our journeys. When we first bought the RV we carried most of our belongings in the basement when we moved to FL.
The original carpet was replaced with plank wood flooring that is much easier to maintain and better for the slide rollers. The slide rollers got brittle over the years and had to be replaced, which was tricky but quite feasible to on-going support from the Newmar support line that will help you get almost any replacement part. I had a leveler spring snap on one journey and Newmar support knew the exact replacement needed and set two springs to our next destination for a reasonable charge.
Required routine maintenance has been pretty minimal. We have had the fuel filters replaced (needed at least once per year due to marginal fuel at some stations). The air filter is quite large, but available thru Amazon and easily replaced through the interior engine hatch under the rear bed. Oil changes are pricy but rarely needed.
Overall we have been very happy with the Newmar Mountain Aire and look forward to many years more of service out of this solid motor home.