When I attended Central's CDL program, both of my bunk mates were in the refresher program. They both went out with trainers and both completed the program. The one I still talk to just signed a lease and is making some good money (albeit, while assuming ALL the risk). It is definitely an fast-paced course. I think they are only out on the pad for a week, with some classroom work mixed in.
I do believe the hours out with an OTR trainer are less than what fresh CDL graduates go through, but don't quote me on that.