The main problem with running a Pi on a microSD card isn't write endurance, it's low quality controller and firmware implementations on the cards.
Contributing factors include:
- Even when used read-only, the flash memory occasionally needs to be refreshed, which means the controller needs to shuffle data.
- Controllers have to map drive addresses to flash, and they store their tables on the flash. Firmware bugs, power interruptions, or problems with the flash can render the tables unreadable and lose all data.
- Some controllers even store their firmware on the same flash that is used for user data. So problems there can brick the card.
Contributing factors include:
- Even when used read-only, the flash memory occasionally needs to be refreshed, which means the controller needs to shuffle data.
- Controllers have to map drive addresses to flash, and they store their tables on the flash. Firmware bugs, power interruptions, or problems with the flash can render the tables unreadable and lose all data.
- Some controllers even store their firmware on the same flash that is used for user data. So problems there can brick the card.