On my 'Benz, I did AIO + 2xSG Thanksgiving weekend.
About 3 weeks ago, I washed it, decided that it had lost a little of its 'dazzle', and reapplied the SG (no AIO). The car looked every bit as good as it did in November.
Unless there are some blemishes in the paint (maybe due to bird droppings, road salt, etc), I wouldn't think that it would be necessary to go back to AIO.
Even reading the bottle, SG can be applied directly to a new car - without the AIO step first. This would lead me to believe that the AIO is more of a cleaner/polish, and would not be necessary every time you apply the SG.