My friends' mothers who had surgery & tablets decades ago - had to take them for 10 years. These days, 5 years is more the recognised time line.
I guess if you WANTED to go for longer once the 5 years was up - that would be recognised .... the hope being that you won't need in excess of 5 years!
All the best for your Onc meeting, @Sister . You'll have read of lots of peoples' reactions to various AIs ..... keep in mind that not EVERYONE gets ALL the side effects ALL the time!!
Fingers crossed that you don't get any (or many!) ;)