"...45 minutes to erase a 16C5x part? 2 or 3 minutes (for the _5X_ parts) is
to be expected on a reasonable eraser. May be you should be doing some more
experimenting or perhaps you do have a problem after all."

  I can confirm this phenomenon.  Most of my PIC16C54's erase quickly.  I
have a group of PIC16C54A's (date code 9429 -- mask CCT) that require at
least 10x exposure.  I marked them, use them for slower development cycles,
and let them relax in the eraser, while the other chips are in & out in a
timely fashion.

Happy Holidays,
  Marv