It completely varies. I've had shifts ranging from four hours to eleven hours - that depends on what flights and how many legs you do. Some weeks you'll be flat out and others you might be on home reserve and not get called out at all (and hours vary from base to base too). It is relatively quiet at the moment across most bases, but before the quiet period I was working 140 hours each month since I started. Last month I did about 110, with almost two weeks of home reserve with no call out. You'll definitely need to keep this in mind when budgeting as no week is the same.