Even those doses have the same name, we custom design each dose based on the application.
For the iPhone, we user shorter (and adjust for power) to create a shorter mobile dose.
For the computer player, we use "pure" doses, longer sequences containing only a white nose carrier and the beats and can be anywhere from 15-60min long.
The MP3s and CDs contain ambient backgrounds in addition to the beats, and are typically mid-length, somewhere between what you get with iPhone and computer dose files.
You will just have to experiment and see what works best for you