Jon Gunnison documents some things that have made pattern libraries successful at Allstate. Tidbits I found interesting:
There are specific jobs (part of what he calls “governance") for maintaining the library. I love that they are called librarians. A "designer librarian" and a "UI dev librarian".
Acknowledgment that there are "snowflakes", or single instances that don’t fit into a pattern (at least right now).
The pattern library is fed by information that comes in from lots of different places.
Pattern Library Workflow is a post from CSS-Tricks