I used to think DS5 had ADHD because of his constant talking, asking questions, low desire to repeat activities or games, and other behaviors.  I was certain of it, until it was dismissed as a diagnosis (for now at least) by the ed. psychologist during testing.  After doing some reading on G kids, I wonder if that is the cause for his behaviors.  Him either needing constant information/verbal stimulation, or maybe just how his brain needs different things.  
I'm starting to feel a little overwhelmed at times.  This behavior was always present (constant talking every minute he's awake), but I find myself having lower tolerance for it as I get older and am less able to multitask.  I call for quiet times (no talking until X activity is done) just so I can concentrate.  This will work occasionally while driving or when I need to get something hot out of the oven.  Usually at other times it's ineffective for more than 5 min.  Another poster mentioning her DS making sounds reminded me of DS.  Though my DS has random squeals while excited, the talking is usually worse for my concentration because I can't ignore talking.
Any tips or just random parental/gifted advice?  I've instituted a "play time" immediately after school to help DS burn off energy, we walk to and from school, and I try to limit TV but he still gets more than I'd like.  Will this decrease as DS gets older?  Should I start to enforce quiet times or just hope this will improve?  TIA!