It looks like the red or gray banner (which offers to change a confirmed reservation to within a 30-day window, at no additional cost) mostly appears between Friday-Sunday, or over a three-day period. So, again, if you are seriously thinking of taking advantage of the offer, don't delay; otherwise, it might change to a "Now you see it, now you don't" scenario. Of course, if bookings continue to increase, we don't know when or even if the offer will reappear this year. So far, Southwest has consistently been posting the offer, for different upcoming months.