Personally, I hope never. I am in one right now and there is no such thing as "brotherhood" but a grift to drain the corp like a stuck pig to the point of death. It's extremely annoying not being able to fix the problems you know exist because it's not in our contract. Or the DEEP fear of automation because my coworkers refuse to learn new skills and are timeservers and do nothing because they are protected.

If you can avoid it, stay as far away as you can. The gains do not outweigh the cost.

Rant over.