not to play devil's advocate here, but she has a point. right now your kids are as safe as they can be due to your knowledge of the matter... hanging out here for hours a day isn't going to make them significantly safer, unless the paradigms as we know them suddenly shift and there is radically new safety info available.
but more importantly, if we are to be truly obsessed about our childrens' safety, our obsession should not be so narrowly focused on car seats, since carseats alone are not the be all and end all to a child's safety--they are but one piece of a large puzzle regarding a child's overall automotive safety. there are far broader subjects pertaining to automotive safety that few people here bother to venture into (sadly, for me), such as keeping up with routine safety inspections of their vehicles, knowing they have safe and effective tires inflated to the appropriate pressure (almost 50% of americans are driving on under-inflated or over-inflated tires!!! that is a major safety hazard!), knowing that your lights all work correctly, etc...
so to say that you are obsessed about your child's safety SHOULD imply that you are obsessed with ALL these things, not just carseats. carseats alone are but one safety device in a long list of items necessary for your child's safety.