I can only go back in history until 1/1/2009. Here are the only two items in my history:
2/1/2009 - 100,450 miles expire
3/24/2009 - 606 miles flown.
Therefore, I must not have had any activity from August 2007 until February 2009 (not really that long all things considered). I probably checked my mileage balance during that time. I obviously have not checked my balance since at least 2/1/09 or I would have seen the expiration.
The recent email I received is because the 3/24/09 miles are close to expiring. Not to beat a dead horse but it would have been nice to receive an email like that a year ago. (Remember the line in Dr. Strangelove where he yells out: "of course the whole point of a doomsday machine is lost if you KEEP IT A SECRET"
)