Assessment practices in higher education institutions tend not to equip students well for the processes of effective learning in a learning society. The purposes of assessment should be extended to include the preparation of students for sustainable assessment. Sustainable assessment encompasses the abilities required to undertake those activities that necessarily accompany learning throughout life in formal and informal settings. Characteristics of effective formative assessment identified by recent research are used to illustrate features of sustainable assessment. Assessment acts need both to meet the specific and immediate goals of a course as well as establishing a basis for students to undertake their own assessment activities in the future. To draw attention to the importance of this, the idea that assessment always has to do double duty is introduced.