My experience with students is that the transformation from reach truck to sit-down is easier than sit-down to reach. The steering tiller and joystick are much more difficult to learn than a steering wheel and control levers.

I do not believe that we can tag the amount of time since evryone is different. The theory is almost the same except for a few operational rules, but the driving, now thats a different story.

As I said, I cannot specify a time on this one.