State of residence for healthcare

For 10 of our 15 yrs of FTing, we were under the 'medicare age'. Over that time we domiciled in FL, TX and finally for 8 yrs in SD. Our D/L etc were from those states. We also however for all those years kept an address in our old home state. We 'rented' a closet in my brother's home and used that address for our continuation insurance. Pretty easy to do. Whenever (rare) it was necessary to write the ins company we merely used my brother's return address. When using 'foreign' medical services, like a hospital, we'd put in our PMB mailbox address and annotate it as "mail forwarding address only". We would try to obtain one medical service each year in the insurance state. I got a letter about 5 yrs in from my insurer noting that most of my claims were via other states and wondering about the PMB address. I replied that we were retired and took frequent trips to see kids, friends and places of interest and that, like my insurance company which uses a PO Box for premium payments, we also elected to have a mail drop where we could conveniently obtain our mail no matter where we were at the time. Even more legitimate today no that mail services will scan incoming mail for you and then open and scan the contents of pieces that you request and trash the rest.