@McTag,
A translator has the luxury of time on his side. He/she can sit at a WP with a stack of dictionaries and grammars at the elbow and polish sentences so that the translation is precise and even elegant. As long as a deadline is met, that's fun work. The interpreter has no such luxury. He/she has to know the exact right word, the appropriate colloquial phrase, the hard-to-translate local expression right there, on the spot, while the other person is still speaking in a different language. That is why, in most government-sponsored assignments, interpreters are assigned in pairs. One person can't do it for much longer than, say, 20 minutes. You don't run out of verbal steam but your mind starts to get fried. So you turn it right over to your partner for her/his 20 minutes of brief fame while your cranium cools.