On Dec 13, 2018, at 11:54, Stephan Guilloux <stephan.guilloux@crisalid.com> wrote:

Stress test still running on reputable brand with no PB, after 6 or 7h.

During this stressing session, we found a few broken SD, from another reputable brand. 
Not all cards, though, but enough to put some confusion... ;-)

Well, remember, we are dealing with flash RAM here. After enough write/erase cycles, it *will* wear out. The goal is to optimize the overall system to get maximum lifetime out of the media. For example, on our production setups we do things like putting ‘/var/log’ on tmpfs (it doesn’t matter for the particular application that the log data evaporates after reboots). That greatly reduces wear on the media, while still allowing log data to be accessed during a session for debug purposes.