Aha!

Had more success with google using some search terms from your reply. From Racing NSW's site:

Meeting Day	Nominations	Weights	Acceptances	Riders
FRIDAY	11am Monday	4pm Tuesday	9am Wednesday	Noon Wednesday
SATURDAY	11am Monday	4pm Tuesday	9am Thursday	Noon Thursday
SUNDAY	11am Tuesday	4pm Wednesday	9am Thursday	Noon Thursday
MONDAY	11am Tuesday	4pm Wednesday	9am Thursday	Noon Thursday
TUESDAY	11am Wednesday	4pm Thursday	9am Friday	Noon Friday
WEDNESDAY	11am Thursday	4pm Friday	9am Monday	Noon Monday
THURSDAY	11am Friday	4pm Monday	9am Tuesday	Noon Tuesday

This is circa-2006 info though, so whether the timetable is the same post-Benchmarking (or from state to state) is another thing. Poking around the Racing NSW site the timing still seems about right though.

Seems to indicate a max 4 or 5 day break between racedays before a new rating would be in effect.

Can't imagine it happens terribly often though. Doubt I just found my fortune...