Working TFC over on small volumes - Their playing again, page-31

I note that TFC is about 36m shares short at the moment. Now do these shares not have to be bought back at some stage? Does this not put upward pressure on the share price? Thus is now not a great time to buy this stock, if you believe that intrinsically the value (NPV of future cash flows) is greater than $2?

How long can the shorters actually stay short the stock? As long as they are able to borrow scrip I presume? This does come at a cost though.....