When I do research, I have to read everything. I don't take abstracts from my assistant. She gets the documents and I read them. And you have to read everything and mark it up and organize it, and then you have to read it all again and make a plan, make a card index. And then you have to plan it.
Planning takes longer than the writing.
I'm slowing down these days. I spent a year just writing this book. I wrote the first draft of The National Dream and The Last Spike each in three weeks, when I was young. Can't do that now. The second draft took six months, of course.