Evidently the "first" treatment has to be two weeks apart, just because the first spray kills the adults but not the eggs they've laid. Of course, if you don't catch the new adults fast, they, too, lay eggs.
I had two that my mom watered for me while I was out of town.... ooops..... they rotted. But I did save a couple of leaves and have them under a plastic dome to see if I can get my pretties back....