I have noticed that even good brand shoes will start to separate their rubber or plastic sole for me at the toe. I use Shoe Goo and lots of clamps for 24 hours. Eventually it might start to pull away again, and I redo it. Not the greatest but extends the life well beyond normal, since all of my shoes come from thrift shops and are already pre-loved. I don't think in this consumer age things are meant to last, so I override that in most cases because usually I am crazy about the design. Birkenstocks are the only product I usually don't have to mess with, but I have even glued one pair that was about 10 years old.