Originally Posted by TaxiApple
You guys got me worried.
I just called NW. It was changed in 1999 to no expiration.
I believe CO is the same (no expiration)
Look, this is just a semantics game played by NW and CO. Your miles do not expire, but your account can be closed and you forfeit your miles. This is not technically "expiration" but you lose your miles all the same. I already quoted the CO rules above. Here are the NW rules (also quoted by
the_traveler above):
If no mileage from any source is posted to a WorldPerks member's account for three consecutive years, the account is subject to termination, including forfeiture of all accrued mileage.
Try asking them about account closing due to inactivity and see what they say. If they still say no, point out the clause in the T&C and say, does this mean this is not valid? If they say yes, make sure you get it in writing!
Note this policy is actually worse than most other US airlines, but actually looks better on the surface. Most other US airlines only require mileage activity. NW and CO say they actually require mileage posting.