ZIH to Barra de Potossi

Just off airport grounds around the corner (coming from Centro) is the combi location for Playa Blanca and Barra de Potosi. Runs either every 30 minutes (week days) and (I think) every 20 minutes or so on the weekends. (More traffic.) Not sure when last collectivo stops running either from the airport or Barra de Potosi but I've caught one returning to the airport from Barra at 6:00pm.