> My understanding is that flash memory does not do very well at all for long term unpowered data retention You need to let flash cells rest before writing aga

> My understanding is that flash memory does not do very well at all for long term unpowered data retention You need to let flash cells rest before writing again if you want to achieve long retention periods, see section 4 in [1]. The same document says 100 years is expected if you only cycle it once a day, 10k times over 20 years (Fig 8). [1]: https://www.infineon.com/dgdl/Infineon-AN217979_Endurance_and_Data_Retention_Characterization_of_Infineon_Flash_Memory-ApplicationNotes-v03_00-EN.pdf?fileId=8ac78c8c7cdc391c017d0d30d6b064f5 https://www.infineon.com/dgdl/Infineon-AN217979_Endurance_an...