For me personally:
Been here 6 years, have 14 to go, at 30%. Unless it's a carrier that has more than 1 type (not big shiny jet syndrome, it just makes NB more junior), and a base where I live I'm staying.
Everyone needs to make up their own mind, but moving because things haven't moved in the past is the wrong way of thinking. What you need to do is try to make the best educated guess what will happen in the future. Most of the legacies have very low growth plans but high retirement. NK has very low retirement but high growth. If 80% of the group will retire in the next decade (AA) you are set, for you to reach the same spot at NK we need to get to 10K pilots. Not impossible, but by no means guaranteed either. If I was 5 years younger and had 2 years less on property I would still leave for any of the big 6. Any FO younger than 40 should keep their options open IMHO.