From what I can tell, that depends on with whom you talk. Some people saw the issue IMMEDIATELY upon opening it, some people saw it after some sort of an intense game session, but was able to clamp it back to the glue and saw no more issues. Other people, such as myself, still haven't seen it after weeks of ownership.
I'd say, you have it now, try not to worry about it. If you notice it, you notice it and it's a problem. If you don't notice it, then no problem!
Enjoy your N7, and welcome to the "family"!