A method in a non-volatile memory, which includes multiple memory cells that store data using a predefined set of programming levels including an erased level, includes receiving a storage operation indicating a group of the memory cells that are to be retained without programming for a long time period. The memory cells in the group are set to a retention programming level that is different from the erased level. Upon preparing to program the group of memory cells with data, the group of memory cells is erased to the erased level and the data is then programmed in the group of memory cells.