I think an AA has to be continuously considered at least yearly. So in the Boglehead world you do your ISP and it calls for some AA and maybe some actions (change as you age). Then that becomes a stone tablet? Well maybe not but some people think that.
But were you so brilliant as to understand your total risk tolerance, the market history, etc when you set up your ISP? The market evolves and even investment instruments evolve. Examples are TIPS becoming available in the last 20 years and before that index fund proliferation. And we evolve in our thinking. I know I am a different investor then I was even 10 years ago.