As far as I know, I am the only one who has done a study to determine the best ways to zap and in the process, I found that a lot of people zap improperly.
I have also seen some zapper sellers provide bad information to sell more zappers.
I have never seen anything that shows that it is ok to zap for less than 7 minutes. I have not seen anything to show that it is ok to zap less than 3 times in a row with 15 to 20 minute resting periods between zappings.
Granted, some get away with doing less, but sooner or later, it catches up with them.
As for the silverado, terminator, etc, while they are popular and do work, the electrodes are both too small and too close together to produce optimum results.