Hey
How many writes are possible to perform on the Secure Storage sector before wearing it out?
Flash memory isn’t really designed for long term storage, although your mileage can vary.
Somewhere, once upon a time someone pulled the number, ‘100,000’ write cycles out of thin air. My own experience is that I’ve had flash memory slowly die in as little as 1 year of moderate use, and I have other memory modules that are still usable after 10 years.
All this to say, it’s flash memory. So probably more times than you might imagine, less times than infinity.
According to the STM datasheet:
The endurance of the internal Flash memory is a Minimum of 10k cycles over the full -40C to +125C temperature range.
The data retention at 10k cycles at 55C is 20 years. 1K cycles at 85C is 30 years.
There are no Maximum erase cycles listed. So I would assume after 10,000 erase cycles you are on your own.
Your best bet for long-term permanent memory would be external FRAM memory on I2C or SPI. Virtually unlimited erase/write cycles.