And yes, it normally takes months.

I see the difference between the White Tower and the Seanchan training methods for female channelers as this:

The White Tower would teach you precise control over rather miniscule expressions of the Power; it would be like being taught to knit one day, then being asked to make increasingly elaborate patterns the next day. The Aes Sedai train more for scontrol, precision and dexterity, which is part of the reason it takes years for them to reach their full strength. There are Sisters that have been channeling for years that are no match for Egwene, Elayne and Nynaeve if it came to fighting with the One Power because they aren't used to handling the large flows that usually constitute the stronger combat weaves. One of the more common duties of initiates is to heat tea to the Aes Sedai's varying specifications by modifying the flow of Fire.

The Seanchan would constantly ask you to perform difficult feats involving working at the height of what you can handle. Over a month's time, Egwene knew how to fuse stone, make explosions, sense movements of the earth and then explore her ability to delve the earth. And that was just with one flow. Working so hard at the utmost limits of their current strength quickly forces the channeler to reach her full potential. They seem pretty good at gauging how much of the Power can be used before it's dangerous, because the rates of burnout among damane seems pretty low especially if a more experienced sul'dam is conducting the training.