Did you happen to read that piece going around about how short sniff walks tire dogs out more than long marches? I saw something on a dog training blog about that a while back, and it said letting a dog stop and smell everything for 15 minutes can wear them out as much as a 45 minute trot around the block. That stuck with me because it kind of backs up what your vet told you. In my experience older labs will tell you pretty quick when they have had enough, and two short walks give them a chance to rest in between. Your mileage may vary since every dog is built different, but I would trust the guy who actually looked at your dog's hips over internet rules any day.

That is such a sweet story, and honestly keeping the lid makes total sense (I would've done the same thing). It's wild how a tiny doodle from someone who doesn't even know you can land right when you need it most.