Winter lines always suck at 9E, summer lines will have a lot of flying. Given that, since NW has pumped so much flying into our schedule in such a short timeframe, even Feb. and March lines are packed with an abnormally high block/line.
For the 10-12 days off line, expect to see a week of hi-speed, then a variety of 1-4 day trip, with 2-3 days off between work weeks. But i've seen line quality deteriorating(probably due to contract negotiation), with a lot more 10-12 days off line, and a lot less 13> days off line. When you see a 8 year captain has to bid a 14 days off line, something's not right. But i hope the line will get better when summer arrives.