Glue ins, the weak link is obviously the glue.
Specualtion is just that.. What happens when the glue breaks down? how can you tell? is it 20years, 30,50,100???
Is it? I thought that once cured, the glue is stronger than the rock itself, and you're more likely to break the rock than the glue bonded to it. Can't remember where I read that, though.