some classes are 3 days, it depends on the model and level you are learning. The more advanced classes take a week.
I took the I3 class that covered all electric models that had that system in it, that was a week long class and the test took several hours, part of it was hands on and the rest was online.
The hands on part i think was our trainers way of verifying you knew what you learned.

To get trained on all models it would take quite a while ;o)
Generally the dealership determines which classes they want you to take depending on the trucks in your customer base. No need to take classes on trucks you don't work on (their thinking not mine).
If i had my way i'd take em all ;o)