As far as limitations... It does count to your station RTU's (right to use). Not really.... but I suppose it depends on what you plan to do with them. Another example of usage is... It is a good way of having a "dummy" station setup... stattion type, button mapping, COR, COS etc... So you can duplicate the "dummy" extension. Sure you could do this off somebodies extension... however has it been changed or not since it was first setup etc...
Thanks,
Wildcard