I found FOT was okay, but yea maybe I did get a little bored towards the end, but that might be more to do with the structure of some of those missions than the number of them.
I think it would be good to have a lot of missions, but maybe in order to make it more fun make a lot of the missions quite small and easy. Like for example it would be fun to have a mission later in the game where you have to stop a hoard of bugs from attacking a town. I like the idea of using heavy weapons on roachs and scorpions
![Smile :) :)](/../../xencustomimages/smilies/icon_smile.gif)
At one point you could fix the towns defense laser turrets, maybe they need activating through an underground bunker.