I've never grown hydrponically so I'm no "expert" but I'm getting ready to in a few weeks when I get my seeds. As far as going on vacation, based on the same research I've been doing as you probably, I would think you'll be alright if you have a timer set up just right. All you would have to do is fill up the resivior and off to your vacation you go. Personally I'm more worried about timing the flooding cycles correctly.
Growing in the attic with the temperature would be a problem I think. Maybe you could build a box and insulate the hell out of it with a high R value. Just a thought. Anyway...good luck.:thumbsup: