There are a few factors that may explain what you are seeing. First, different baits do have different food bases and different active ingredients, so sometimes one formulation is just more attractive to a rodent populaion than others. Another explanation - which sounds like what is happening here - is that the rodents are eating the bait you have put out, but you are just going through less bait. The active ingredient in Final Blox is more aggressive than that in Contrac, so it is very likely that the rodents will die before eating very much bait. Both Contrac and Final are single feed baits (the rodent only has to feed on it one time to consume a lethal dose), but since the rodents have more time to feed on Contrac before they die, we will sometimes go through more bait.
As long as you are seeing the signs of rodent activity diminishing, then we would continue to monitor the area and supply fresh bait as long as you are seeing rodent activity.
It would be recommended to change Final Blox Rodenticide out every 40-60 days if not eaten. Very cold or warm temperatures will mold or sour the bait faster.
We recommend checking stations baited with Final or any other rodenticide at least every 30 days, or more often if you have known rodent activity.
Final Blox Rodenticide has a shelf life of 1 year once the pail is opened or 2-3 years if kept sealed and out of extreme temperatures.
EPA Regulations require Final Blox Rodenticide and other rodenticides that contain second generation anti-coagulants be sold in quantities that are a minimum of 16 pounds. There are other professional baits that are available in single 4 pound pails. We carry neurotoxin baits such as Fastrac Blox or Gladiator Blox, and first generation anti-coagulant baits, such as Ditrac Blox.