Line bidding at XJT with ILIW and SLIW windows allows pilots at ANY seniority level to improve (often VERY signifigantly) their awarded line however well or poor they bid or were awarded. It is not uncommon to change your line value 20 hours up or down or move from zero weekends off to almost every weekend day off. Generally, feedback ive heard with PBS is there seems to be almost zero open time and very little opportunity to change your awarded line in any signifigant way.