If the added working time has much value they'll find a way to compensate. This way it simply means that you can't force a fastfood worker to do closing shift and then still clean after they've done their work.
Outside of the pure "pair of hands" work there is a lot of evidence that more working time doesn't increase productivity.
And, really, life is about more than just work. No need to allow companies to slowly erode the rights previous generations of workers have fought for.