When they need one. Buddy (now deceased pitbull mix) had two fractured canines that needed extracting. Then, a year later she spit out a molar and when they knocked her out to extract the roots, they X-rayed and found she had resorptive lesions and needed 15 extractions. But on the surface, her teeth looked great for an 11 year old dog! She gave no indication of trouble. After that she realllllyyyy needed another cleaning but she couldn't have GA any longer. Obi (boxer mix) is six and I'll likely do a cleaning next year. He doesn't really need one but I'd rather be proactive. My parents' dog is an eskie/beagle and she's having a cleaning in a few weeks. She's eight.