[ATM] Looking for the best PWM cycle time for dew heaters

[AMaroney@sptimes.com]

Has anyone figured out the best pulse width modulation (PWM) time for a 
dew heater controller?  Specifically, how long should one 100% cycle be?  
If it were too long the dew heater would noticeably cool off before 
heating up again (running at less than 100%), but is too short a problem, 
say a few dozen cycles per second?  I was thinking of using a PIC16F88 
(yes, a 555 could do it also) and some IRF510s as the 12v switches. 
Thanks.

Allen