Originally Posted by Stefan Daystrom
Almost all airline's miles expire EVENTUALLY if you have no activity (say, for 3 years). For a true frequent flier that sticks to one or two airlines (and their airline partners), that's typcally a non-issue. But I think the point of the poster you were replying to was that a vast amount of miles are awarded to INfrequent flyers who sign up for FF programs "just in case" but then forget about them and/or never have "chance" to fly that airline again before the 3-year (or whatever) expiration period is up. (These are people who don't choose the airline based on the FF program they belong to, they choose solely on price and/or convenience, and only earn miles if they "happen" to fly again on the same airline. Thus "by chance".)
Thank you for explaining my point more clearly than I did
I was thinking of the accounting practices regarding outstanding miles, and the fact that companies were not really showing them among their liabilities. Given that the FFP membership are generally free and that airlines often try to enroll you in their program, I suppose many people end up with a lot of miles on many different airlines, never reaching the threshold for redemption. For them, miles are probably free, but they can rarely use them anyway. So "award tickets" are rarely "free tickets".
Good points on another post regarding iDine. I didn't know of this program, and it sounds interesting for someone in the US.