Unpowered SSDs can lose data over time; QLC NAND retains data for about a year, while TLC holds for 3 years. Long-term storage with SSDs isn't reliable—consider backups with other mediums. Regular access to SSDs is necessary to prevent data degradation when storing long-term.
https://www.xda-developers.com/your-unpowered-ssd-is-slowly-losing-your-data/