Methods, systems, and apparatus, including computer programs encoded on computer storage media, for enforcing a decay policy for a data object. One of the methods includes receiving a request to store a data object in a storage device; obtaining a user policy identifying a lifetime of the data object; determining, using the lifetime of the data object, a voltage policy for a plurality of memory cells of the storage device, wherein: each of the plurality of memory cells will store one or more bits of the data object; the voltage policy identifies a voltage to provide each memory cell; and an expected time at which raw bit errors of the data object will cause the data object to decay is equal to a time point identified by the lifetime of the data object; and storing the data object in the storage device according to the determined voltage policy.