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".)
I used to be one of these INfrequent flyers, but after 3 LHR-NRT flights on differing carriers (within 9 months) I did my own maths:
typical cost of flight with cheapest carrier: £450 ($820).
Typical premium to fly with *A carrier: £50 ($90) - but can be less.
Which means that after 5-6 flights I can get an award flight at a 40% discount. (roughly 5x£50 means I paid about £300 for a 'free' flight)
Miles aren't free at all.
But the 20kg extra baggage allowance... I can't put a price on that!!