I noticed where you said that advantage is the best flea medication for indoor pets. What about bathing them, is it not true that bathing a dog removes the affect of the medicine? I have a Yorkie and a Shih Tzu and the yorkie constantly urinates all over himself so not bathing him for a month is not an option.
The more frequently you bath the less effective the product. You may want to consider an oral flea preventative such as Program. vetcare