All depends on the crowd and what's happening during said period of time.
We recently did our annual OP Woodsman. First mission started at aprox. 12 AM, ended officially Sunday morning, supposed to end Sunday at noon.
We had a bit of down time, some missions were volunteer base and it went great.
Nobody crapped or burned out.
IMO - Too many milsims try and cram in as much as they can get.