Often? I think you're confusing rare instances that are reported on, as frequent occurrences. For every innocent guy freed on new evidence, there are potentially 1000's who aren't. The evidence it takes to overturn a guilty verdict has to be of the no doubt variety, and even then. The State does not like admitting mistakes. How many innocent guys you think are rotting in prison who you will never hear of, and never see such evidence brought to light? Quite a few, I'd imagine.
Now of course, you can use that reasoning for a case against the death penalty. I'm just saying that LWOP isn't much of a compromise, and as much you could say that the State fucked up and killed an innocent man if they do execute the wrong guy, you could say the same for guys who served their lives in prison and died there. In both instances, the State still took their lives, and you could even argue that the LWOP guy suffered even more.