Artificial companions are a new type of technology that is changing the way people interact with intelligent systems, by trying to build and sustain long term relationships with users. To evaluate such systems the typical usability methods for system evaluation are not enough, due to the need of accessing aspects such as social behaviour, emotional sensitivity and personalized interaction over long periods of time, with very specific users. In this paper, we describe the (full) design cycle of a companion system, arguing that a user-centred approach is the more appropriate, taking into account the referred specific issues. As such, to help us focus on developing a companion system for the prospective users, we based our design in the archetype of actual users – a persona. Furthermore, we brought this same concept into the evaluation phase in order to access the companion performance in a long-term interaction.