Originally Posted by soitgoes
That depends on the program. Some programs simply expire the miles and keep the account open; others close the whole account.
My Amtrak "miles" expired after 3 years of inactivity. (I had enough points to go approximately from the front of the train to the rear, for free)
The account, however, remains open. I guess as long as there's still a valid e-mail address associated with it, they will still send you their marketing materials.