Unfortunately there is really very little "standard data" I can give you about this, for the reason you also mentioned.
At the moment there are approximatively 40 trainees in the different stages of the program. New spots are opened up based upon the progress of the existing trainees in such a way that the Instructors can handle the inflow. This way we ensure that all trainees can participate in the program without the Instructors being overloaded with work. This is beneficial both for trainees and Instructors (trainees do not have to wait a long time to receive assistance and Instructors have the time to provide assistance without being hasty due to a huge workload).
As for the time it takes to complete the training: again this is difficult to say. Some trainees have lots of free time to spend, others have also a busy "real life" (job, family, and so on). Besides that, everyone has a different learning curve. Some pick up things fast, other prefer to take their time to digest all information. Suffice it to say, do not expect to finish the program in a couple of months, because that is unrealistic. We want to ensure a complete and high-quality training with individual assistance and that takes time.
Finally, it is a good idea to bookmark the Admission page and check it often (I know this from experience, I checked that page for a month or so multiple times a day before I got admitted back then
I hope this information helps clarify things for you!