Taking as its point of departure, situations arising in classrooms exposed to a heavy use of CAS, exemplified by the Danish upper secondary school mathematics program, the paper discusses the use of "old" cognitive frameworks of mathematics education as an alternative to more recent theoretical developments in the field. The paper draws on three rich examples of CAS use in relation to the following: mathematical concept formation; mathematical proofs and proving; and classroom teaching. Each of these examples illustrates aspects of CAS use that appear better captured and addressed through "old" frameworks. This includes the mathematics specific learning difficulties that a heavy CAS use gives rise to; the inexpedient use of CAS in proofs in textbooks; and the tacit norms and contracts surrounding CAS use in the classroom. The paper thus serves as a call to continuously consulting our research back catalogue, also when addressing problems and challenges which at first sight appear "new", such as the constantly evolving digital technologies for learning and teaching mathematics.