Pretty much, training achieve us all in the short run, and considering we are in our twenties because from a certain age on the body doesn't respond the same way it did. So in a way fighters do have to take advantage of their youth to do this, sure.
That would really take a toll. Maybe in my younger years I would have been able to, but even then I am sure that I would be regretting it immediately.
It does take a toll no question there, and that is why fighters retire so soon, the body cannot deliver any more, it's depleted. That is why they earn so much as well, as it's not the average guy who has the capacity to perform so often at such a high level.