You should define it every year. (specially if you working in tech). Best if before or after large projects. You could define two visions, one for your company

You should define it every year. (specially if you working in tech). Best if before or after large projects. You could define two visions, one for your company itself and one for whom your company is working for. V1: "Make our company more desirable, fun and a nice place to be"" V2: "Make facebook a friendly place for children" Missions have a tendency to be useless and cheesy. Try to keep it close to your reality. Example: "Deploy a basecamp killer" Be careful not to sprinkle your vision/mission with strategy or values.