i agree about getting them out in layers
the last ones to go are hiding in the deepest tissues
are the hardest to reach
if you wait too long to follow up, they will have a chance to multiply and recolonize
best is just long enough to let them hatch out, as hatchlings are most vulnerable to the herbs
if you haven't corrected the problem than enabled them to infect you to begin wtih, you are still vulnerable to reinfection