The golden rule is: use -Werror for Debug builds, so you catch and fix all warnings during development. That's fair enough. But never ever leave -Werror enable

The golden rule is: use -Werror for Debug builds, so you catch and fix all warnings during development. That's fair enough. But never ever leave -Werror enabled for building in Release mode. You'll be preventing your code from building as soon as a new compiler version goes out. Maintainers or code archeologist will have a much worse time than if this option was simply disabled to start with.