last summer during a 5 mile tail hike the soles on both of my hikers separated from the top forcing me to shuffle the rest of the hike with literally no support on my foot. I bought new hikers when I returned but the damage was done.
When I returned home, after limping around for several weeks, I was diagnosed with multiple stress fractures on my right foot and spent the rest on the sumnmer and early fall wearing a medical boot.
I have other keens come apart in that way but never sustained a serious injury. The glue you use seems to fail after a while, usually without warning and if you are halfway up a mountain like I was, there's not much you can do.