The answer appears to be: 

1.  Living hinges will not work in ABS more than 1-2 bends because it is a crystilian whatever chemistry big words stuff etcetera etcetera type of material (unlike polypropylene and polyethylene). 

2.  Living hinges will not work in the harder versions of PLA, because it is too brittle.

3.  No one seems to have tried to making living hinges with the "rubbery" form of PLA yet, so that might work.

However, if you really need an ABS living hinge, I imagine you might be able to cover ABS living hinges with urethane adhesive which would help it retain function after the ABS fails (ie because it would now be a composite).

Good work on the research.

1.  Living hinges will not work in ABS more than 1-2 bends because it is a crystilian whatever chemistry big words stuff etcetera etcetera type of material (unlike polypropylene and polyethylene). 

2.  Living hinges will not work in the harder versions of PLA, because it is too brittle.

3.  No one seems to have tried to making living hinges with the "rubbery" form of PLA yet, so that might work.

However, if you really need an ABS living hinge, I imagine you might be able to cover ABS living hinges with urethane adhesive which would help it retain function after the ABS fails (ie because it would now be a composite).

i use printed hinges for the door of my solidoodle enclosure (vertical door) without problem.... and for a lot more than 50 cycles... (10 cycles per day for near 6 months ...)

but if it's hinges for a real door... it's another story...

I know it's been done look on thingiverse for hinges
http://www.thingiverse.com/thing:45731

The thing is you can't make it so short that it folds on itself at a sharp angle or you'd get eventual wear and thinning.  But you should be able to do something along the lines of the link and make it work for a while.

We have done them before, but they have to be on the thicker side.

The thing is you can't make it so short that it folds on itself at a sharp angle or you'd get eventual wear and thinning.  But you should be able to do something along the lines of the link and make it work for a while.

Any advice is greatly appreciated!