It can ping pong one way or the other due to personal preference. The average line value (ALV) is set by the company, and can between 72-84 for the NB fleets, and is the same for each seat/AC comination across all bases (NYC 737 CA is the same as ATL 737 CA, etc). The 12 month trailing average of that number has to be between 73-78. The actual average of all PBS runs for that position have to be within 1.5 hours of the ALV. The line construction window, which is pilot controllable to some extent, is plus or minus 10 hours of the ALV, with a minimum pay for line holders of 65 (even if the awarded line is lower) and an upper limit of 91.5.

What people do after that is highly variable.