Perhaps this applies? On the Sell Your Images page... We ask our contributors to maintain/keep online a minimum of 70% of their approved/accepted submissions for at least 6 months.
Or, in the Faqs Disable Images You can disable all files approved more than six months ago at any time. You are allowed to disable 30% of files uploaded in the recent six months however 70% must be kept online for six months from their approval date. You can disable each of your remaining 70% after the six months pass. Once files are disabled, nobody but you or the admin will be able to view/access them. The files will remain in our offline database until all liabilities concerning them are cleared off, then they are automatically deleted.