Gaylord, that is a big "It Depends".
Tournaments get 3 games played in less time than that, but they will often call games before they are done, and give little time for terrain and deployment, etc.
We tend to chit chat, take long lunch, etc. Also depends on points.
If we play 2K points, we should be able to get in 2 games.
If we play 1K points, and don't waste time... maybe 5 games. (Especially if play on 4x4 tables.)
I just like to play, so any pt value is fine with me. Warboss just likes 2K because then he can use all 4519 models of his Ork army. :D
There are supposed to be 3 or so missions for each race, I think the tyranid ones are: