Rocket Lab took about 7 years for Electron: for the first ~5 years after founding they did some sounding rockets and DARPA/ONR-funded non-orbital-rocket propulsion tech before pivoting. Can't remember or find when Peter Beck said they started on an orbital rocket, but they got NASA funding to do a study of the concept December 2010 [1]
[1] https://web.archive.org/web/20110723113333/http://www.rocket...