Things are pretty fluid right now at DCA. We shrank the base when AA brought PSA in to do some of the flying. Then we picked up UA pairings and theoretically there is supposed to be Delta pairings at some point. Anyway, to answer your question, for Feb's bid month, it shows the most junior line as an 8/16/16 hire, so he likely spent at most 3.5 months on reserve including IOE.

But.... Feb is a slow month for lines, there will be more lines as we get into the peak travel season. Also, looking at the cover sheet, we have a total of 87 FOs listed, but 22 are still in training. For someone hired Dec/Jan might not see any reserve by the time they finish IOE. For someone hired today.... who know, but probably not too long. Maybe 6 months max? DCA is junior right now.