UTP Baluns For HDTVI

What is the maximum "practical length" of cable below which good picture quality should be expected running HD TVI Cameras. I know there are voltage drop issues for the power over the same cable but what is the length that the video signal can reasonably handle assuming CAT6 cable is used.

I'm not interested in an IP vs TVI discussion just the use of HD TVI Cameras with baluns. 

Thank you.

Yes I had read this previously. I was just wondering if there was a more definitive answer like "Don't use baluns over 100 ft" or whatever. it appears to be a real suck it and see situation. Would I be correct in saying that?

its analog, so its not gonna cut out all at once. so probably depends on your tolerance for degradation.

btw, there are also these: