@dalias well, fwiw, USB flash tends to be just about the least reliable storage medium we have nowadays!
In any case, no matter the medium, it's going to degrade over time, so there's no point in relying on the robustness of any particular storage device... if you want reliable uptime, you need RAID, and if you want data integrity, you need backups. There's just no way around this.
In my view, the only actual gain from solid state storage is performance, not reliability. So it's HDDs for me!