You know, Drinking caffeine (in tea OR coffee, or anything else for that matter...) increases your resistance to it. Meaning, if you drink too much before long you'll need to drink more for it to have to same effect.
Which is the main reason I don't drink coffee, only tea because there's less of it. ( I know tea LEAVES contain way more caffeine than coffee, but thats the leaves, not the drink.)
So I would assume that starfarers don't consume caffeine, because they'll end up costing more than it's worth.