Disposing of old boxes

By “dispose of” do you mean “sell or give away”?  If they intend to do that, they absolutely need to make sure the boxes are up to date (which they should be if they have been used very recently) and they need to be removed from your parent’s account. If those things aren’t done - especially the latter - the boxes will effectively become bricks, since DirecTV says there is no way for the boxes to ever be used by anyone else if they are still associated with another account (and they claim they can’t disconnect them from an account).  I don’t know how to disconnect a DirecTV streaming box from an account (I don’t have one) - hopefully someone else will chime in with that info. Once those things are done, a factory reset would be a good idea - then they could be safely sold or given away. 

If they just plan to throw them away (which would be a waste), then it doesn’t really matter what they do - as above, the boxes would be bricks anyway. 

Thanks