Did all 12 starships have 5 year missions?

[Forbin]

Oso Blanco said:

Christopher said:
All we know is that one starship had one five-year mission

I'm not even sure about that one five year mission. Has it ever been addressed on screen, apart from the voiceover in the opening credits? I don't recall anyone ever mentioning a five year mission.

Only peripherally in Mark of Gideon, where Kirk tells Odonna that the ship has food and supplies for 400 people for five years.