Mike,
I would get a copy of the Lardy Retriever Journal articles volume I just to have a second description of the training. I have recently watched the Smartwork Basic Handling DVD recently, and I also reread the Journal Article on the Double T. In some instances, I imagine the Double T is finished in less than two weeks, or up to a month. Maybe what is said in the Smarwork DVD includes more than just the Double T. It might includes 3 handed casting, force to pile and all of that.
There are a lot of things that could be done on the Double T to make it easier for the dog if someone wanted. I went to seminar, and the trainer said he was disappointed if he got through the Double T with a dog without having a refusal of some sort. He said he would rather it happen in the drill than later in less controllable circumstances.
I'm not saying this is the way to do it, but someone could identify the piles before casting to them to the point where the dog just does them through habit. You can make the sessions so short, and incorporate fun bumpers so that a dog is not stressed out at all. You could go out and line to the pile from up close only twice inbetween doing two overs, then throw some fun bumpers and stop for the day, and do something similar for everyday in a week if you wanted. That would definitely draw out the time.
I'm just saying that not everyone follows every move that is on a video step by step especially if they have some other information, or past experience to go by. I'm a complete novice but thought maybe I had something to add. To give an example of how complete a novice I am, when I get something like slow flaring sits on the double T, I'm not sure I know what to do about, and just ignore it for a good while.