The Age of the Both/And CEO - Conversation Starter - HarvardBusiness.org:
"1 to 5 recipients = 2 to 4 revisions
5 to 10 recipients = 8 to 12 revisions
Company-wide or to Executive Committee = 30 to 50 revisions
Even the simplest missive to one person benefits from a couple of extra passes, and if it's going to the management committee, expect everyone to have changes (and changes to those changes).
Here's a checklist to consider when revising:"