According to Wikipedia:
On August 17, 2007, HBO announced a second season for Flight of the Conchords, originally set to premiere in 2008, but which has been postponed to January 2009. Prior to the announcement, Jemaine Clement stated in an interview with The New Zealand Herald, "they [HBO] are interested in doing another series but we have to think about it. It's not a definite offer but they have talked about us starting writing but we've got other things we want to do as well". Bret McKenzie has stated in several interviews that the band has used up "97 percent" of their old songs in the first season. In an interview with The Star Ledger, he said "We'd need some time to develop new material. It's like the second album syndrome. It might take a lot longer". Shortly after the renewal announcement, Clement stated in an interview that the second season would likely consist of fewer than twelve episodes "so they could concentrate on 'quality not quantity'". McKenzie and Clement plan to write for the second season in Wellington, New Zealand, before they return to New York City in 2008 for filming.