We've all noticed that after each PC, TV interview, public appearance and other events discussing the murders that there is a surge in tips. In the past on other cases, I've heard LE state that a case is not cold because they are still getting tips.
I don't how many personnel are still on this task force. The last I read was a couple of months after the murders LE was downsizing from as many as a 100+ to 10-20 personnel. If they still have a 1st sgt (Holeman) supervising I can imagine they still have multiple individuals involved. These are resources that could be used elsewhere if this murder was not still heavily pursued. Sooner or later, if it hasn't already happened to some degree, I imagine Superintendent Carter is going to have to answer questions in the state capital as to the resources being devoted to this investigation and the impact on the department budget. As long as he can say we got x amount of tips last month and this brings us to y amount to date he can probably keep justifying the resources. At the 3 year mark or even at the 2 and a half mark I would not be surprised to see something to keep the case rolling through the media and certainly there is a possibility of more evidence at the 3 year mark. I know it sounds cold, but at a certain point there is going to be more pressure to justify resources. (Of course, all this assumes the status quo in the rest of the state. If some tragedy - a terrorist attack, a massive weather event such as numerous tornadoes hitting multiple counties - strikes then the pressure to divert resources from the investigation is going to increase.) Speaking from a resource justification point of view, these public appearances generate the tips that in turn continue to provide justification for personnel resources. 1st Sgt Holeman even said in one interview that anyone listening is interested in LE put in your application to the ISP because they need people.