You must not have been listening in the right places. It is far beyond just counting days. State revenue departments chasing escapees are doing things like checking where your dentist is located, where the vet for your dog is located, and other fairly subtle indicators. This is in addition to looking at obvious stuff like your driver license and where you vote. Anyone considering fleeing for tax reasons should consult experts in the destination state and cut all possible ties to their previous state. Be sure to tell the FAA, too.
Re two houses we have two; a city house and a lake house in the same state. It's great. It can be a bit of a hassle arranging and monitoring services like lawn and snow for wherever you're not living. Your cute Miata convert will not be much good for transportation because you'll find that you are always hauling stuff (or at least we are). Some of what you'll be hauling will probably be refrigerated food. I hauled a couple of tool boxes but got tired of it and bought a tool kit from a woman who said it was her ex-boyfriend's. My hunch is that he didn't know it was for sale. She met me in a parking lot and had the kit in her car trunk. Nice kit, good price, though.