Orchestral wind players: how important is it for you to know when your partner should be in unison with you?

To know that for a certain melody, the other flutist/oboist/clarinetist/etc. is playing the exact same melody you are, and then at another point he/she's doubling you in thirds or sixths or octaves? What about incidental unisons, like just for a single note at the end of a melody?