I never claimed otherwise. Adult fliers, like many such insects, only live for a few days at most in which time they mate, lay eggs & die. They can't do anything else, because they don't even feed-
http://www.ext.colostate.edu/pubs/insect/05584.html
When those eggs hatch the first instar stage will die if they encounter sufficient BTI in their environment, as you say. Some of the later instars will be killed as well, per the manufacturers information. When more flyers emerge from later stages of development after the first application of BTI, the first instar stage of their eggs will also die if BTI concentration is sufficient. Hence the instructions to apply 3 times at 1 week intervals to maintain killing strength throughout that period of time.
Obviously, the manufacturer will not recommend an inadequate treatment regimen, despite what other sources might say. Of one thing I am certain- application of gnatrol as a soil drench, 1 tbsp/gal/week for 3 weeks eliminated them from my grow. Period. The Victor flycatcher hung in the enclosure has zero flyers on it six weeks after the last application of that strength solution. That's well beyond their 28 day life cycle indicating that all larvae have been killed thus preventing the existence of adults.
