Theories of successful ageing emerged in the early 1960s, prompted by the need for the nascent discipline of gerontology to be grounded in a theory base. Over successive decades various theories have been proposed, none of which has specifically addressed the ageing of people with lifelong disabilities, specifically those with cognitive or intellectual disabilities. It is now established that the adult life expectancy of this population approximates that of the general population, owing to enhanced access to health care, better nutrition, and improved life style. Difficulties encountered by this population include the lack of clear transition markers throughout their adult life. The lack of inter-sectorial collaboration between ageing and disability support services, exemplified by the two Australian Productivity Commission Reports, has resulted in an isolation of people with lifelong disabilities from mainstream gerontological developments. Recent theories of ageing, which incorporate psychosocial concepts, need to be refined in the context of people with cognitive impairments. We argue that such adults can experience an enhanced lifestyle in older age as witnessed by data gathered from them, indicating their understanding of their ageing. We note that this understanding has implications for the development of a more inclusive theory of successful and positive ageing.