well, thats plastic for ya..
at least yours lasted this long...
when I got my 2005, the 'hinge' is actually duct tape... been that way for an undetermined amount of time, but more than the 2 months I have owned my vulcan.
in the end we can probably blame the bean counters on the lack of hinges (as well as many other cheap alternatives installed at the factory.
they were designed to last for a couple years, which they do. after that, warranty is gone, so the manufacturer has no more stake in the bike.