Ant baits generally begin to take effect within a few days of being placed, though the time it takes to see noticeable results can vary quite a bit. Factors such as the ant species, the presence of other food sources, and the surrounding environment can all play a role in how quickly they work. As for how long they last, ant baits can remain active for several days to a few weeks. Their effectiveness largely depends on the severity of the infestation and where you place them. Putting bait stations in areas where ants are frequently seen will maximize their impact.