In this chapter, we focus on longitudinal first-person research methods in HCI. First-person research involves data collection and experiences from the researcher themselves, as opposed to external users (or participants). We present three projects where longitudinal ‘auto-approaches’ to research and design in HCI were applied, namely one auto-ethnography and two autobiographical designs. These projects help illustrate the benefits and challenges of using these first-person research methods in longitudinal HCI and interaction design research. We conclude the chapter by reflecting on themes and lessons that resonate across the three projects (i.e., range of participation, data collection, time to reflect, concluding).