I almost lost miles myself due to inactivity too. Think it was the early part of this year that I made note of the expiration date of the miles after logging into my account. I set up a reminder to purchase miles to keep the account active.

Well, I just noticed that I must have ignored the reminder that went off on June 1st. So I logged into my account today and the miles are still there. But the expiration date can no longer be found. Don't understand the point of some airlines doing away with the expiration dates in the account details. Does it cost them anything to keep the account and miles "active" indefinitely? Delta does this apparently. Just curious...