BOS has approx 287 pilots right now. 95 are in their first year. Using that blunt data the guy who showed up a year ago is approx 1/3 up the list. If everyone upgrades by seniority he'd be in the top 1/3 of FO's. Trust me, his perspective is going to be VASTLY different than the guy who shows up right before the influx shuts down. That guy will struggle to get off of reserve. This has happened multiple times in the BOS base history - locked down, big influx...and the guys at the tail end look at the same names ahead of them for decades. If the company plans to keep increasing the BOS base even then, at some point, it will slow down and then you're back to hoping for retirements or you can start sending the senior guys chain saws, 'vote no on motorcycle laws', etc.