After the hinge repair described there, those old sunglasses have been working fine and I use them regularly. The screw recently worked its Loctite loose and was held in largely by blind faith.
It’s obvious why:
A tiny dab of JB KWIK should solve that problem for the foreseeable future:
In the highly unlikely event I must remove that screw, I’ll just refer to this picture and mill the epoxy out.
The Smell of Molten Projects in the Morning 
That is an amazingly neat dab of epoxy. What did you use to apply it, a toothpick and a steady hand?
Exactly: caught up a dot of goo on a toothpick, watched in the microscope, and managed to not make a mess of it. I’ve learned that a pile of epoxy will flow to fill the edges of a hole, so I heroically resisted the urge to smush it around and just watched while it slumped into place.
Helped that it was a low-caffeine sort of day, too…
Makes that blob glomming the brass angle bracket onto the frame look downright crude, though, doesn’t it?
I know this was metal, but for the future remember that threadlockers have this tremendous delayed-destruction effect on many plastics. They appear to do nothing untoward, then you load the thing and it shatters. Sometimes it takes months for the effect to manifest itself.
Been there, done that, alas.
It’s particularly vicious on acrylic: a few minutes later, you’ve got a pile of pieces neatly separated along all their (previous) stress lines.