The global population is becoming older, and the trend for this shift is only accelerating. At the same time, older adults are using the Internet and mobile technologies in increasingly large numbers. As evidenced by the proceedings of many conferences such as the ACM MobileHCI or the ACM CHI, the usability of interactive technologies designed for older adults is of significant concern. Yet, the methodologies we employ for designing and evaluating such interfaces are largely the same as those used for any other user group. In this position paper, we argue that one methodological size does not fit all especially when it comes to usability evaluations with older adults. We do so by reflecting on our own experiences with designing and evaluating interactive technologies for older adults (particularly for those over 80 years - the "oldest old"). We then propose for discussion senior-centred approaches and adaptations of established usability evaluation methodologies.