My wife has been dealing with this problem for many years. She gets a 90 day RX four times a year. The regulations for narcotics are incredibly complex and differ from state to state.
The RX is good for either six months or a year in Calif. (I can't remember which) but only 14 days in Nevada unless in a pharmacist hands when it is good for six months. If using mail order one must comply with the rules of the state that is filling the RX.
Finding the way through all the rules is challenging. There are many bureaucracies involved; doctor, state (maybe several), federal gov., insurance company, and the pharmacy. Some pharmacies allow individual pharmacists to make up their own personal rules.
So advice about what works for one person may not apply to another.
The best we can do is get a 90 day supply and plan to be back in three months.