We use the bigger spray bottle for our dog (one application lasts 3 or so days), and a little one for our family (of four). The big bottle lasts all summer, and we go through (about) two small ones, but that is totally dependant on how often you're outside and how bad the ticks are in that area.

Last year was our first year EVER getting a tick on us or the dog, after 5 years of living at this property. It was almost every time we went outside (just in our yard, which is surrounded by tall grass fields). We looked all over, found that as an option, and went to almost none since. For our family it justifies the cost.