Actually it really depends on what code-share you are flying under for that trip!
I just finished a 4 day trip that was blocked at 25:51 and we actually flew closer to 27 hours! First two overnights were fairly short, around 9-10 hours, last night was 16 hours. during the trip we had 2, 3 hour sits in STL. I have never been called during my 3 yrs here for any type of reserve duty during these sits. Now this trip was under American connection.
Most American trips are go, go, go! Long days, decent overnights and more days off!
US Airways express, has more long sits between flights. You may sit an hour or more in Pit between legs. You may also be looking at 4-5 hours of flying and then a 16-18 hour overnight!
United Trips are pretty much like American, but longer overnights, we do ORD for 24 hours, but I think it's because they want to keep you legal, I can see that 24 hours go down by 4 or 5 hours just from sitting in the penalty box in ORD a few timew during the day!
Basically all three code shares you will be on duty on average 8-12 hours. Some days it just one leg straight to the overnight, other days its 4-6 legs, but they give you plenty of rest. I'll admit the schedules were better when we had Pref-Bid, but they are slowly starting to improve as we get more pilots on line. We have been really short for the past 4 months with all the new planes coming and no one to fly them!
Good luck, hope this helps!