Thank you everyone else for your comments. You've been very helpful! For those who were interested in the benefits, just one of the things I read:

Feeding only one food for the rest of your dog’s life is a surefire way to help him develop food allergies or intolerances. Any nutrient deficiency, excess, or imbalance expressed in a food can become entrenched in your dog’s body if that’s all he’s fed for years on end.
(“Variety Is the Spice of Life,” WDJ June 2001, for more information about the importance of occasionally switching foods.)

I also talked to a local pet store owner, and she said she feeds her dog the same dry food, and rotates a little canned, which sounds like a good idea to me.

LuvGold00, I am going to take your advice, and try to start rotating when he gets to be a little older, maybe >1 year. Then try the rotation thing every 4-6 months, unless Murphy proves to have a sensitive stomach.

Thanks again everyone!