I've always wondered...If you call them during their off time (either in the evening after they are done for the day, or earlier before they start) and leave a message, do they even check those messages/call back people?

I'm sure a lot of people leave messages because I'll call and leave a message, then try checking back an hour or so later and the mailbox will be full.  But I will never get a call back from an asian provider agency.  But if I call later on, during their listed hours, they will pick up and I can schedule.

Of course this is only for the agencies, as independents most often call/text back.

Anyone know?

They have bookers and if the booker knows who you are
you will get a return call even if you leave a message after hours.
I've left vm's and texts and gotten messages after 9:30 when
the bookers check messages. I guess they call back who they know and
if they can fill the schedule they stop calling. It just depends.

I call when they should generally be answering the phone.  If they don't answer, I seldom leave a message.  Most of the time I get a call back because they see they have a missed call and recognize my number.  If I don't get called back, I'm thinking they probably aren't working.  When I have left messages, they don't seem to call back.

The bookers are usually too busy to give you a holla back, or if it's late they are booked up so they don't bother.  I guess I'm considered a frequent flyer because I RECEIVE text message from bookers, asking if I want to try out a new gal.   Yeah, I'm tooting my own horn.  Like I should be proud of that, huh.