Equity rules say:
Rehearsal days are 6 days a week
And each day is a 7/8.5 which means 10:00-1:00 rehearsal then 1 hour lunch break and then 2:00-6:00. And within the last 10 days they can have a rehearsal day to be 9/11. Prior to opening they can have (on stage) only four 10/12 days.
And as a general rule they can't rehearse longer than 5 hours without a break and on the performance day they can't rehearse prior to the performance longer than 5 hours.
People can correct me if I'm wrong but this is what I learned in school... it can be slightly adjusted to the production but this information is straight from the equity handbook.
"Now the best way to learn the theater, always, is to be a stage manager" - Stephen Sondheim