For direct learning I've found around twenty books 5 books over 4 days most rewarding (though I only do the timeline intergration once on the first occasion). In this case I think you need to find what works for you. I find trusting the process works in my favour. Adding more books... well I let my preconscious processor handle that. I had already put in the request/expectations. The extra books are just more data that my mind can use to strengthen the direct learning.
I had already posted one of my first experiences with direct learning... it was kind of accidental and I've had a few more similar events. http://www.learningstrategies.com/forum/ubb/Forum1/HTML/000037.html
I find I don't really use the timeline much installation. For me it seems to happen as a result of curiosity. Since I search through books and web pages with a wanting to know, asking what can it tell me what's new, what's useful?
Yes, I wrote the stuff I mentioned in that post, turned out 18 pages long. I'm not sure if it will be of much use because of it's lenght.
As a result of direct learning I've written another article of 3 pages on another topic. I have notes for 3 more articles, different topics. Not sure if I'll write them. I just seem to write stuff for the heck of it or to stop the ideas from running around in my head
Just interesting stuff that I've learnt.
One interesting thing I have noticed about direct learning... if I don't use what I was direct learning on it fades,and the results seem much more subtle. Using it, my skills grow in that area. Well thats perfectly lodgical really. It's the same for any skill, using it regularly you get better at it, it becomes more natural. Yet for the other stuff its like 'not' riding a bike for years. I know I know it but I'm not using it... I also know that when I start using it, it will be very easy to brush up on.
For me the experience of direct learning was surprising. I do find the results stonger when I use more than 5 books. 
Alex