It felt like it took me "forever"- but I was trying to do it properly. It took me around 4 weeks and I was easily doing 12 hours a day. But I stopped to do every quiz, to look up the images when he said look at the images, make annotations in First Aid, and look up anything that didn't quite make sense.
Toward the end I got slightly more efficient, but most of the time I was doing 2 videos/day because that got me to 9 hours, and I still wanted time to do questions and review things.
It can probably be done in 15 days- if you want to shoot yourself in the face or if you don't actually participate in all of the quizzes in each lecture.
I personally got a lot out of DIT; it forced me to go through everything, and a lot of the important points were emphasized over and over again so I will never forget them. My qbank is going well, and I can't complain about where I am right now in my studying with a month left.