The panel's max refresh rate is right around 90Hz. The control board can be OC'd to receive a 120Hz signal, but that's not what is actually being displayed. In addition to this, there's all sorts of strange flickering, stuttering, and artifact-esque stuff that will appear. It just doesn't look right if you compare it to a panel made for 120Hz.
As for the dying out early, just need to do a bit of digging. There aren't a lot of "after 6 months with overclocked IPS, I'm still happy" type of reports. People just don't make posts like that in general, which is where people can be lead wrong if they find a bunch of bad reports, as that's the only time folks are driven to make posts about their experience. However, in most forums, there weren't very many people defending their 120Hz Korean IPS screens.
I was an inch away from ordering one of those Overlord displays, but a flood of bad experiences and discussions about them made me steer clear. One day soon, hopefully. Not now though.