We were California residents when we first went full time. Because my wife wasn't yet eligible for Medicare and we wanted to keep her CA based PPO medical plan with national coverage, we kept a CA domicile until Medicare became an option. We used the Escapees Texas mailing service for virtually all of our mail and used our Son's street address for domicile purposes. That meant we filed CA state tax returns and had CA driver licenses and vehicle registrations. After she was able to get on Medicare we moved our domicile to the Escapees service for South Dakota, but kept our primary mailing address in Texas.
HTH,
Art