At a major, flying domestic, probably 9-13 hours per duty day, but it varies. LH guys get in and ride it out. The fewest days per month are ULH guys non-stop DXB, HKG, BOM and they are gone 4 on, 5 off. But Mumbai (BOM) is a 16 hour flight and only the most senior crews are flying them. Southwest crews are very productive and fly lots of 2 on, 2 off months--10-13 hours per day, 6 legs per day. I have several SW friends and they love their schedules.
And you better tolerate getting up at 4 am and commuting to work or coming home at midnight.
GF