I think the key difference isn't the memory, but the recall. Humans can recall memories at will, while dogs often require a prompt or stimulus, and there's not

I think the key difference isn't the memory, but the recall. Humans can recall memories at will, while dogs often require a prompt or stimulus, and there's not a clear indication that they're self-recalling information to think about things beyond a period of persistence. That's not diminutive of them, more a reflection that we've been selecting dogs for this behavior and other "breed traits" (which I think of as specific hereditary OCD) for thousands of years, so it makes sense they're primed for this from a context- or direction-giver. It's why if you teach a dog a trick that it's still able to recall years later, it won't go off and practice it on its own or teach it to other dogs.