There is no need to throw them away! Hakko supports the products we make for many years after the model is discontinued. In your case, the ceramic heating elements (PN: A1321) can still be purchased no and for years to come. This is true for other parts on the Hakko 936 that you may need.
With regards to replacement soldering iron tips, the Hakko 936 originally came with a 900M, 900L, or 900S Series soldering iron tip, depending on the model purchased. By using the new T18 Soldering Iron Tips that come standard with the Hakko FX-888 Soldering Iron, you can get a small performance boost on your 936 thanks to the new design of the T18 tips that optimizes heat transfer. This is a drop-in replacement so there is no need to buy additional parts in order to get this benefit.