Bad news for Alaska Airlines miles holders. The airline just made an announcement to change the life span of their frequent flyer miles. As of April 1, 2008, all accounts without any mileage activity for the past two years will be deemed inactive. As such, all flyer miles on the account will be removed. To keep it active, the account should keep on earning miles. Alternatively, any miles redemption activity also keeps it active.
For more airline updates regarding frequent flyer miles earning or policy changes, regularly check Upgrade: Travel Better.