For mmwhiterose, Siuan was raised to the Amrylin Seat so young for several reasons, most of which I have pointed out pretty clearly in the books, I think. The preceding years had seen a number of Amrylins die after only a short time in office. In New Spring: the Novel I showed one reason why the pool of potential Amrylins, Aes Sedai with experience, was reduced over part of that same period. And then there was the impasse over several candidates, none of whom could gain enough support, so that Siuan became a compromise candidate who was raised in part because various Sitters thought they could influence or control such a young Amrylin. Just as it is unusual for a sister to be raised to Sitter before she had worn the shawl for a hundred years, it is unusual for a sister to be raised to the Amrylin Seat short of having worn the shawl for a hundred and fifty to two hundred years, and above two hundred years is most common.
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