I found a file opening time issue when working under Maya referencing mode.
I have a setup-ready fat sim file, when I reference the file into my Maya scene and save, it takes about 23.5 sec to re-open the scene, but if I make some change on weight (for example sliding attachment weight) and save, it takes about 318.3 sec to re-open the scene.
It seems like ziva spending a lot of time on weight updating, or it is Maya reference updating mechanism..