In recent years, the possibilities and pitfalls of qualitative secondary analysis have been the subject of on-going academic debate, contextualised by the growing availability of qualitative data in digital archives and the increasing interest of funding councils in the value of data re-use. This article contributes to, and extends these methodological discussions, through a critical consideration of how the secondary analysis of thematically related qualitative longitudinal (QL) datasets might be utilised productively in qualitative research design. It outlines the re-use of two datasets available in the Timescapes Archive, that were analysed to develop a primary empirical project exploring processes of continuity and change in the context of men's care responsibilities in low-income families. As well as outlining the process as an exemplar, key affordances and challenges of the approach are considered. Particular emphasis is placed on how a structured exploration of existing QL datasets can enhance research design in studies where there is limited published evidence.