4 years seems reasonable to me. It takes most organizations six months to do literally anything outside the status quo. A general strike is an attempt to organize a coalition of federations of organizations.

Why the fuck would you give four years of warning for managers to document “a slow accumulation of poor performance” and other bullshit to shit can pro-union employees.

This is the reality of striking. The threat and build up to the strike are just as important as the actual strike, because it's about more than just not going to work; it involves complex and wide-ranging logistical question, from how to support the strikers (otherwise corps can just wait you out) to how to decide on a single list of demands.

The very real threats you describe are what make outspoken union advocates awesome and brave people that we should all look up to, and it's why we all have a responsibility to express solidarity and never cross a picket line. Together we bargain; alone we beg!