Traffic to and from Beijing airport over Chinese New Year

We will be arriving at Beijing airport mid-day February 7, 2016, and we will be departing mid-day February 9. This coincides almost exactly with Chinese New Year. With the expected heavy holiday traffic from people coming to and from Beijing from elsewhere in China, how long should we allow for taxi travel between central Beijing and the airport? 1 hour? 2 hours? 3 hours?