Please don't do all these old wives tales things. A good vacuum will take care of the issue. Those sprays are nothing more than marketing items. They do not work. The shampoo's don't even work anymore.
Go to headlice.org and other web sites that will give you good common sense solutions to get rid of them.
They will not be gone for good. They are at epidemic proportions across the USA. They can't get rid of them because that would mean that every person in the USA would have to be treated and their house vacuumed all on the same day, plus they would all have to segregated to make sure they don't crawl onto someone else.
They will be back. Especially if you don't let your child be dirty. Head lice like clean hair. They can live there very well and stick their babies to the hair shaft.
One remedy that I am going to do once the kids start back to school is to get a water bottle, add a couple of drops of Tea Tree Oil in it then add water to fill it. Then every morning when I am brushing the kids hair I am going to use that water bottle to spray their hair to style it. That way the Tea Tree Oil will constantly be on them repelling the lice.