The reason that most do it yourself pest control plans fail is due to inconsistency and the lack of proper chemicals to get the job done. Most people do not have the time to spray their homes for pests and bugs in a consistent enough manner to actually eliminate them. All chemical pesticides (green, and caustic alike) are unable to destroy insect eggs. The pesticides can only manage adult bugs. The pesticide placement process must be consistent enough to kill all adults, and then when eggs hatch, to kill them off before they reproduce. This is known as the egg cycle and even with professional grade product and bi monthly treatments, it can take 3 to 6 months to break the egg cycle completely.
Local and federal governments require that pest control servicemen be trained and certified to use the chemicals that are necessary to break the egg cycle. All chemicals are regulated by state environmental policies and ensure that no chemical be potent enough that it does not break down within a month or so. That is why consistent treatments should be applied for at least 6 months on a bimonthly basis. Spot treating after that is always good because even if you have a pest control service, your neighbors may not.