In a study to  test the efficacy of chocolate milk as a recovery aid, a team at the Indiana University's Department of Kinesiology and Applied Science, Human Performance Laboratory concluded that chocolate milk may be an effective replacement for "commercial fluid replacement drinks" or "carbohydrate replacement drinks" for recovery between high endurance exercise bouts (note 1).
Professor Joel Stager, Director of Human Performance Laboratory told WebMD that the findings suggest that chocolate milk has an optimal ratio of carbohydrate to protein to help fuel tired muscles (note 2).
Another researcher,Jason Karp, told fitnessmagazine.com that chocolate milk provides carbohydrate replenishment for muscles to metabolize unlike water, where there is nothing to metabolize (note 3)
However, drinking too much chocolate milk is "heaty" from a TCM (Traditional Chinese Medicine) point of view and should be accompanied by drinking lots of water.
According to Ruth Carey, a nutrition consultant specializing in sports nutrition, general fitness, weight control and disordered eating, there is a 2-hour window immediately after a workout during which we should replenish and recover (note 4).  So, I am going to take chocolate milk immediately after my workout from now on.
Enjoy your second half life.  This is your last chance!

Sources:
1. Jason R, Karp et.al., "Chocolate Milk as a Post-Exercise Recovery Aid", International Journal of Sport Nutrition and Exercise Metabolism, 2006, 16, 78-91, http://www.milknewsroom.com/downloads/stager_chocmilk_study.pdf 
2. Richard Sine, "Chocolate Milk: The New Sports Drink", WebMD Health Health News, http://www.webmd.com/fitness-exercise/news/20060224/chocolate-milk-new-sports-drink
3. Kelly L Phillips, "Got Milk? Try Chocolate After Your Workout", http://www.fitnessmagazine.com/recipes/healthy-eating/superfoods/chocolate-milk-after-workout/
4. Ruth Carey, http://www.milkpep.org/resources/497_ChocolateChill-Final-Presentation-Ruth%20Carey.ppt

Disclaimer: This posting is not meant to provide health advice and is for general information only. Always seek qualified health professional's assistance before embarking on any health program.