I've worked on site that had a very different result, rather than a glass ceiling of any kind. They were Pandalyzed on the first Panda algorithm release. They recovered during the first Panda data refresh in January 2012. They have now are not simply recovered, they are enjoying record, well-targeted traffic.
Because of this experience I look at many reported recoveries as only partial recoveries. And though we understand more about Panda than we do about Penguin, Panda is still a black box to a large degree. This makes partial recovery a much more common effect than full recovery.
I assume the only reason the site I worked on had such a strong recovery is that their Panda problems essentially came from one major factor that was fixed, and possibly a couple minor ones that were also fixed. It's probably more common for sites to be hitting many Panda triggers in a more major way.