I posted about my (long-gone) parents, but as a parent MYSELF I neglected to answer, so!:
My deal with ANY kids is this: SHOW ME that you've completed anything those responsible for you consider to be more important than [fill in blank with non-productive activity, e.g. playing Halo] and THEN you can do it until you are no longer in that situation. (I.e. Now have something more important to do.)
of course, the argument always rears up about who decides what is "more important," but once the boundary has been defined - which take less discussion than you might think - I see that it's set in stone.