Spot on IMHO
All the points and numbers in this article concur with my experience in freelance team webdev work. 1-3 month projects seem to work best (aim for 1, expect 2-3), along with occasional small updates/fixes on live sites.
The longer a project goes on, the more time it takes to keep track of everything up in the air - diverging codebases, db schemas, artwork, server config changes... which leads to more friction and bugs at deployment time. We forget things. People change jobs. Other projects push long-running projects onto the back burner. That's more than enough to erase any gains to be had by queueing up changes.