Do you know what these chemicals are and how long they work for?

I'm not sure of the chemicals but for fleas...? the first guy dosn't sound like was treating fleas. Most of the time what exterminators do is treat the eggs so they don't hatch and treat the adults so they can't reproduce (create more eggs) since a bugs life is only a couple of months this will usually kill the ones bothering you. As far as how long they will last it depends on haw quickly the ones outside the sprayed area can overtake the affected area. If you have pets that go outside the treated areas it will mean a shorter time. Most of the chemicals base their long term effectiveness on how fast an insect will overtake the affeced area.