—-#1) For offices of which there is only one office holder at a time (e.g., Prime Minister, President, Speaker, Governor, Mayor, etc.) only the current office holder is formally addressed with the forms of address of the office. Forms of address are courtesies of office just like the big corner office, great parking space and preferential seating at events. The courtesies stay with the office, and don’t become the property of former office holders.
They go back to Mr./Ms. (Surname), Congresswoman (Name), Representative (Name) … whatever is their preference and is pertinent to the office they currently hold.
—-#2) Offices that are held by more than one person at the same time are different. In those cases, (e.g., Admirals, Senators, Judges, Professors, Ambassadors, etc.). former and retired individuals DO continue to use their former honorific. Having two ambassadors or two senators in the room is not confusing.
—-#3) The individual is flattered by the honorific inflation. But when you ask them directly, they say ‘It’s not formally correct.’ Having been the singular office holder they know what it’s like to have all the formers clinging to the courtesies of office.
– Robert Hickey