Some interesting tidbits when you start looking at which AS on each level should be Deferring to her equally strong sisters ... some of this doesn't really "jive" with the books, but it seems fairly clear that most women don't seem to expect an equally strong AS to defer based on years in Training or Age either, comes down to force of personality IMO.

Having an official role and how long they've been in it is clearly a bigger indicator between these women, even when it's not "official" that someone has been placed above others.

Level 13 (most senior to least senior based on training and as necessary age)

Elaida (goes down to being older than Moiraine and Siuan)
Moiraine (she's a year older than Siuan)
Siuan
Romanda (3 less years in training than Lelaine, but 2 more than Elaida, Moiraine and Siuan)
Lelaine

Level 14 (most senior to least senior based on training and as necessary age)

Bera (she's a year older than Kiruna was, but they had shortest training after Elaida/Moiraine/Siuan)
Kiruna
Martine Jenata (older than Leane, same amount of training time)
Leane
Sheriam
Liandrin
Pevara
Aisha
Valera
Sashalle
Yukir
Galina
Merise
Saerin

Level 15 (most senior to least senior based on training and as necessary age)

Nesune
Carlinya
Talene
Myrelle
Morvrin (same amount of training as Desandre, but 1 less year as Accepted)
Desandre
Lemai
Anaiya (older than Katerine, but same years in Training)
Katerine
Theodrin
Silviana
Shemerin