I go by the porch light thing too. That is when I apply the permethrin + imidacloprid drench. We never had grubs in Hawaii when lawn care practices included as needed applications of diazinon.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738