Reusing boiling chips
According to this post at www.reference.com/science  


  Boiling chips are generally porous, trapping heating bubbles and
  allowing solvent vapors to form in the air cavities. They should
  always be added to a solvent prior to the beginning of a heating
  cycle; adding to a hot liquid may cause it to violently boil over.
  Boiling chips and stones are only used once, as the absorptive
  material becomes impregnated with the first solvent used in.


And Wikipedia confirms the basic idea of why they shouldn't be used more than once:  


  The structure of a boiling chip traps liquid while in use, meaning
  that they cannot be re-used in laboratory setups.


From personal experience however, I have to disagree with these absolute "cannot be done" sort of statements.  I used to rinse the used chips in an appropriate solvent and then heat them at some temperature well above the solvent's boiling point overnight and don't remember ever having problems. 

I realize that the boiling point isn't completely relevant when you can have porous, high surface area material with adsorbed solvent.  Also, as I stated in the comments, I don't remember using PTFE coated chips.