If I exercise vigorously enough to get winded (SOB), I am able to cough small amounts of brown mucus, which in my experience, is the older, deeply trapped stuff. I feel this is important to do, so even at my age, I really try hard to get winded. At 76, I can't go briskly walking on the ice in the winter, so I bought a rebounder and do the best I can with that. Also, I noticed that the brown mucus doesn't have the small plugs anymore (as it did when I was new to this game) so I believe I have kept those airways open pretty well.