Hi Jpdkmd,
Welcome to the Heartland Owners Forum. There are quite a few of us living full-time in our RVs, including myself.
If I remember correctly, Landmark, Big Horn, and Big Country models are all warranted for full-time residential use. They offer a residential refrigerator, the Yeti cold weather package, and dual pane windows that all contribute to a better year round experience along with many other features that all add up to a comfortable living arrangement.
Our Landmark pre-dates the residential refrigerator, but I'd love to have one.
New Landmark 365s have a number of other features that are very attractive for full-time residential use; 3 air conditioners, an induction cooktop, a dishwasher option, a Power Control system, and much more.
If you have more specific questions, please feel free to ask.