Google announced on Twitter that they will be automatically deactivating accounts with no spend in the past 15 months. Google said this will help “speed up your AdWords experience” some how. Google added that if your account is deactivated, you can always reactivate it when you are ready.
Google posted a help doc on this:
If your AdWords account has been inactive for more than 15 months (meaning your account hasn’t spent in more than 15 months) your account will be automatically canceled. Note that there are other reasons an account can be automatically canceled.
What you’ll see
When the account is canceled, you’ll receive an email notification. As always, you’ll be able to log in and access your canceled account. You’ll see an in-account notification letting you know your account’s been canceled.
You’ll always be able to reactivate your canceled account. Note, however, that if you reactivate a canceled account, but the account remains inactive and does not serve ads for three months after reactivation, the account will be automatically canceled again. Learn more about reactivating canceled accounts
Keep in mind, accounts that are canceled will not be accessible via the Google AdWords API. You’ll have to reactivate the account before attempting to view data or make changes to the account via the API.
Forum discussion at Twitter.