By George!

I think I've got it!

http://www.sciencedaily.com/releases/2012/04/120402093940.htm

Here's the original reference:
Too dog tired to avoid danger: Self-control depletion in canines increases behavioral approach toward an aggressive threat
Holly C. Miller, C. Nathan DeWall, Kristina Pattison, Mikaël Molet and Thomas R. Zentall
Psychonomic Bulletin & Review
DOI: 10.3758/s13423-012-0231-0

Here's a perfectly good explanation for some of the "zoomie" issues I'm having with Tess.  She's an active, bold, independent puppy and I require a LOT of self control from her.  By balancing my need for her to practice self control, and making sure that when I'm asking a lot of control from her (such as during agility practice) I haven't "depleted" my available store. 

I notice that if she's been a down stay most of the day at my side, she practically explodes with energy and I'm setting her up for failure to ask for tasks that require a great deal of control.  I always reward  when she chooses to practice self control - but there's only so much that can be asked of 13 month old puppy who's still building that pool of self control. 

I think that for now I'll be very conscious of my goal for the session in regards to self control - Am I working on increasing her amount of self control?  Is it a play session to restore her brain after a long training session and thus I'll ask a minimum amount of self control?  Or is it a "working" session with equipment or other tasks that require her to draw upon that reservoir of self control?

Hope this made sense - I'm still noodling it through in my mind, but I'm on the verge of an "ah-ha" moment.  I think :)