I've done about 3 walks with a friend and her lab but the last few weeks have been busy so we'd not seen them in a while. I met her today and Molly was straight away over to the dog wanting to play! Molly is a very timid pup and usually hides behind me when we meet other dogs so she must remember Bella! I was amazed!
Oh yes, they have marvellous memories. When Sparky (nine weeks old) came to spend the day with us I was getting him to sit for photos using my iPad, with treats. A while later, I picked up the iPad and he sat nicely! He'd associated the two in no time. Our Guide Dog pups remember us four months after they have left home when we see them for the last time before they are matched with their owners. They jump all over us ...
I think memory lasts a lot, lot longer. My two saw the breeders - at our house - six months after we brought them home and went nutso. They only saw them for about ten minutes then. Then, we saw them again another six months later, at their house, and they had the same reaction. The definitely remember their daddy mum and dad as well as the humans, as they behave very differently towards them than any other dog.
We have had Coco for 9 months now, last week we were up at the ManxSPCA (where he came from) for training, and there was one of the kennel staff chatting with the trainer when we arrived. Coco went bananas to greet her, he hasn't seen her in all that time - they do have good memories.
We picked Baxter up last year the week we were going on holiday to Yorkshire. He was just 9 weeks and as you can imagine everyone who met him just loved him, no one more than the landlady of the local pub who would take him off us to get cuddles and to show him off. If he heard her voice he would get so excited We went back last October and at 6 months old he could find his way to the pub! he wouldn't want to walk past it which was a pain as it didn't open sometimes till 4pm. We're on holiday just now and as soon as we went in she shouted his name.. he was beside himself lol.. It would be rude not to visit often
I also think their memories are great - I know it was only a week but the two dogs we walk with in the morning were on holiday for a week, and their mum's car was left with us - each time we went out of the front door Bailey would go to the car and whine and bark (as he does if the girls are in the car). He was beside himself when they returned to get their car - including going mad seeing my friend and her husband!