Thoughts on the need for a 4-Season insulation package?
Arctic Fox by Northwood is considered to be a four season coach-- fifth wheel or TT.
There are many other considerations that differentiate a TT from a FW. Level floor throughout is considered by many to be a plus for a TT as is the ability to be towed by a truck, van or SUV. If you tow with a truck you will have the entire truck bed for stuff and that is not a small consideration for extended stays in the trailer.
Fifth wheels tend to have a little more storage, are often considered over a TT by full timers, and some say they tow better. They typically are heavier, cost a little more new, and have a higher cargo carrying capacity and gross weights.
Many that full time move with the seasons; therefore, the extra insulation package is less important.
The typical rule of thumb for recreational users is about 1500 pounds of stuff, water, propane, etc. in the coach. For full timers it is about double that. Be sure you find a coach that has the carrying capacity for what you will need. There are several good sites that are devoted to the full time RV lifestyle with a lot of good information. You might check out Escapees, LovemyRV, NvRvers, Technomadia, Gonewiththewynns, etc.
One last consideration is to find a coach that is built for full timing. Not all are.