We will do our best to cache your Derivative Images for as long as you specify in your Cache settings. However, the sheer number of possible image permutations that imgix enables you to create makes it impossible to perfectly cache all of your images forever.
At times, we may evict image derivatives from cache and re-render them as necessary. We will not bill you for derivative images that are evicted and re-rendered before the lesser of their intended cache timeout or 30 days.