I know that i'm some newbie on the forums lol. From what he said it sounded like there was a shelf life to an engineers turrets by which I mean they quite working on there own after a period of time without any of the typical methods.
I was a noobie once too I'm not a walking encyclopedia either Wraith and HORSE know a lot more about the game.
Maybe they'll add a time limit to balance the game or something. Or maybe they already did.
The only thing we can do is read all reviews, watch all videos and listen to other people. A lot of stuff is still speculation at this point.
Edit: new hands-on: http://news.filefront.com/pax-2010-hands-on-with-brink/
I like this part:
Then the leaderboard popped up. I had 41 kills and 12 deaths, which as I said was the best on the game. And yet, by score, I was right in the middle of the pack. Why? Because, Rahdo Ham told me, leaderboard score is determined by a variety of factors, including team support. As an engineer, I could buff my teammates weapons, but I didn’t do it enough as I should have. Ham pointed out how a medic was above me on the board because he basically spent the entire game running around healing folks who had been taken down.