Nope you are completely wrong on this point. Like I said use the RIGHT filament and there is absolutely no reason this can't be done.

The colorfab xt would easily give you thousands of flexes. I haven't got any left or I'd prove it.

Also polypropylene comes in a3d printable filament, that too would just keep on working.

And if you want a brilliant example of a lifetime living hinge (well dozens of them actually) look no further than the one piece grabbing hand:


You need to wait till you've got your 3d printer and have used some of these filaments before making such sweeping statements :-)