MicroSD cards are very reliable to store data. This reliability decreases over time and with heavy usage. The timespan a card is expected to securely store your data is called "data retention". For the cards provided by us, a very conservative estimate of the data retention is 25+ years when stored below 55°C (130°F).
The data retention is refreshed when the data is rewritten. As it is best practice to verify your backup from time to time anyway (also to make sure you can still find it), we recommend to periodically verify you microSD card backup, e.g. once per year. You can easily do that directly from within the BitBoxApp, with the microSD card plugged into the BitBox02:
- Plug your microSD card into the BitBox02 and connect the BitBox02 to your computer.
- Start the BitBoxApp and unlock your BitBox02.
- Go to "Manage device" > "Manage backups", where you see a list of all backups on your card.
- Click on "Verify backup" and compare the name and backup ID shown on the BitBox02 with the data in the BitBoxApp.
This process also redundantly rewrites the backup file on the microSD card, extending the data retention period.
Please be aware that it's good practice to avoid single point of failures. It's more important to have multiple backups than to optimize a single one.