Yes, that is still a legitimate concern. My last phone died because of the flash memory wore off. We’ve seen some failures on the flash of the previous Turris. The flash in omnia should be a better quality than the one in most routers (where it can fail after few thousands of rewrites), but we still don’t want to risk it.
If you are willing to put the strain on yours, you can configure to have another copy of the logs somewhere else, we use syslog-ng, so just drop another config file into /etc/syslog-ng.d/.