William H. Patterson Jr. has blogged about the latest edits to his Heinlein biography —
Some time in 2014 — nine years after I finished it the first time — we should have volume 2.
Part of that time was spent expanding the text and dividing the manuscript to make two volumes instead of one, an idea ultimately abandoned:
In the spring of this year , midway into David [Hartwell]’s first set of edits for this volume, he brought up the possibility of splitting this volume into two books, giving a three volume biography in all. There was some back and forth; ultimately David decided not to go forward with a third volume, and since he gave me the word late in August, I’ve been working ever since to cut the manuscript back to the same size as volume 1. Possiby with the idea of a third volume in mind, David had asked for an expansion of the text that utimately accounted for about 400 pages of new manuscript. The expansion itself was not particularly demanding, as I had cut much more than that out of the manuscript in 2005 and 2006 — but it was neither possible nor desirable simpy to restore the old version; the expansion incorporated all of Hartwell’s edit.
Cutting a 1400+ page manuscript back to about 1000 pages is a time-consuming and finicky process involving several passes through the entire thing.