At DAL we have PBS and incorporate a ALV (Average Line Value) number in to the PBS run each month. With the line holder guarantee at 65 hrs, the lowest ALV is normally 72 and the highest 83 or so. They can construct lines plus or minus 7.5 hrs from this number they put out monthly.
In the winter months I have seen a slew of lines at 66 hrs and in the summer I see a ton of 89 hr lines.
Line holders can White Slip (WS) open trips that pop up. With our duty rigs a two hour turn pays a min of 5:15 and the same one hour down layover and fly back pay 10:30 so there is a way to make money without flying a ton of block. Seniority in the seat helps.