As a hobbyist who relishes building equipment from hairy string and sealing wax
I can recommend using a small "sun lamp" for erasing PICs. I have thus far
successfully erased a 16C54 approx 50 times without harm. I have physically
separated the uv and ir parts of the lamp. It takes 20 mins in a single session.
I am reluctant to move the chip closer to the lamp as the chip gets quite hot -
this effect has been reduced with the application of Typpex to the chip! I dont
suppose this method is covered in Microchip application notes but it works for
me! Incidentally I have noticed that the high end memory takes longer to erase
with the exception of one location about a third up which takes longer still. I
notice from discussions here that the write cycle is more likely to determine
chip life than the erase cycle.

Martin