If you are a Partner Edition customer, then one of the features of this cost-concious plan is that the data sets expire after 30 days. As such it is not designed for sites that require a high volume of flights at regular intervals over a sustained period of time.
If a data set is expiring, an indicator will appear next to the data set name once 9 days remain until expiry, and will remain there after that data set has expired:
If you feel that a data set is incorrectly expiring, please contact email@example.com
Cheers from the Propeller Team