Bull. It's called ghosting, not persistence, and (someone correct me if I'm wrong, but) the only macs that exhibit this behavior use LEDs for a backlight, so the useful length of the backlight should be forever.
the only macs that exhibit this behavior use LEDs for a backlight
Glad my TV doesn't do that.
My rMBP with the LG panel indeed suffers from image retention. But: the only way to actually notice it is to have a checkerboard pattern on the screen for around 20 minutes and after that switch to a dark background. I have been working with this machine for quite some time now and so far, could't find a situation when it was actually an issue (or even detectible) during my normal usage (both in work and gaming) - and I usually have static UIs, like TextMate, open for a long time. If all the other machines are like that, then I honestly don't know what people are complaining about.