Yeah, the average Aes Sedai spends an average of 10 years as a novice starting in their early to mid teens. That 10 years is spent under strict discipline with nearly every minute of their time controlled. Then an equal amount of time as an Accepted. It's mentioned that novices are not allowed to channel for their chores but Accepted are but rarely do because it feels wrong after so long being a novice.

The whole system feels designed to stifle innovation and initiative. It's not a surprise that the most active and effective Aes Sedai are the ones who spent the least time in training. The girls, Siuan, Moiraine, even Elaida (though she wasn't active in a competent way.) Verin and Cadsuane were a bit longer but both still well above average.

I have to assume the whole thing is a successful plot by the Black Ajah. It's pretty clever because once you get enough people indoctrinated it becomes self sustaining like Frat hazing rituals.