The various ad sites have various subscription periods, some monthly, some quarterly, etc., and they don't always line up together as far as starting and ending dates.  The girl may finish her tour dates and the booker just leaves the ad up until the period it was paid for expires.  If the girl is on a short vacation and the ad was purchased long-term, they will also leave it up because its already paid for they won't have to pay again when they return from their break. Different ad sites give price breaks for longer-term ads.  If a girl is going to be here a few months, it may pay her to buy a three-month ad rather than pay for two one-month ads back to back.