I can thoroughly recommend puzzles, especially for a senior sheltie. My Revel has several different games, the latest being the Nina Ottoson Tornado which he loves. http://www.amazon.co.uk/Nina-Ottosson-Dog-Tornado-Activity/dp/B001KZ8FWE I spend so much time training the younger dogs and apart from going on the walk, there is only a limited amount you can 'do' with a dog of this age. So he doesn't feel left out after I've done training/working the youngsters I settle down with the puzzles and Revel has a great time sniffing out the treats and it also gives him a bit of a physical workout too. For a cheap simple puzzle option, I saw a great idea a couple of weeks ago at a show. They had a rubber doormat, the thick lattice ones so the dirt drops through that are for outside the home. http://www.floormats.co.uk/floormatting/rubber-entrance-mats/rubber-mat-octo They put treats in the gaps and the dog sniffs out the treats and has to get them out.