Comment by gleenn

Both can be true. I have specifically heard that shoe glue needs to be repeatedly compressed to be maintained or it will disintegrate. Anecdotally as well, I had a pair of quality, lightly used, but old, hiking boots that had the sole completely separate after a day of heavy use. The runber sole completely detached from the leather shell inner shoe. The crazy thing was that BOTH boots failed within 20 minutes of each other.