About 6 weeks overseas, working 6 or 7 days a week followed by almost 6 weeks off at home, travelling on your own time shaves a few days off the time off.
The monthly hours depend upon the country you are in or the client's restrictions can also dictate. An annual average of 300 to 650 hours seems to be the norm.
I'm happy with my lot in life although more money would always be welcome!