I have to say I have a TON of experience teaching a 10 day multi type of course. It is actually how I originally started my own business way back when. I had a 90% pass rate. I interviewed my students and if they didn't meet my criteria, I told them to expect it to take longer. I was working with 2-3 students per month. Is it tough to fly an AVERAGE of 4 hours per day (plus time for taxi, start up, etc)? Sure. But compared to my traditional students at the end of their training, my 10 day students were leaps and bounds ahead.
When you teach in an accelerated manner, it is full immersion. I liken it to going to France to learn to speak French. Sure, could you take a course once a night at a local college for 6 months? Yup. But in one month in France on your own you are going to be speaking and understanding French at a much higher level.
As for student's attention span, with over 3000 hours of flight instruction given, I have come across 2 people in that time that could not fly an average of 4 hours per day. Most students wanted to fly more!
Again, accelerated training at any school is not for every student. But for those who are looking for full immersion, a 10 day instrument course is the way to go!
Michael