With regards to those looking for course date swaps seniority is everything in BA. It governs your fleet movement in future, time to command and in general your quality of life when it comes to 'bidding' for your work.
With lots of movement in the company followed by stagnation your mate who joined just a year ahead of you could quite easily get his/her command or move on to something bigger 4-5 years before you down the line.
Obviously if its for a degree or something equally as important I wouldn't suggest dropping out with a few months to go but from the time you join to the day you leave your seniority is everything.