I appreciate you both taking the time to respond. I'm relieved to hear that's how senior dogs normally are. He's acting lazy, really - not sick. I think I'll try the Iams senior formula, though. I've been giving him the Purina One senior formula. Maybe a change in diet will give him a little more umph.

More frequent walks couldn't hurt, either - though he doesn't seem to enjoy them much.

He was such a hyper puppy - and it seems like his "puppy stage" lasted over 3 years! Then he finally got manageable and more trainable, and just generally a more enjoyable dog. It's kind of sad that doesn't last long before they slow down.