It's another "scr*w the customer" move, plain and simple. It costs DL nothing to maintain a bunch of customer accounts for an extra year (or even several years). Seems obvious that SkyMiles had one of their analysts look at the number of miles that expired with the 3 year expiration rule, extrapolated the figures to a 2 year expiration, and then showed the figures to a beancounter somewhere. The beancounter's eyes grew bigger, s/he danced around the office with glee and showed the figures to his/her boss, it made the rounds in the CFO organization, and finally up to Grinstein who made the pronouncement that, henceforth, SkyMiles shall expire in two years.