For a long time people have collected mementos; items kept as reminder of a person, place or event. Practices of memento creation are constantly changing; for instance through the accessibility of digital photography. Still, we most often create mementos of special occasions such as weddings or holidays. However, besides these milestones, we cherish certain experiences from our everyday life. This paper describes a cultural probe study exploring which memories of everyday life become valuable. Our findings confirm that seemingly mundane experiences can become valuable. More specifically, a memory was seen as valuable if it: was regularly repeated, had social value, continued in the present, influenced life, was exemplary of character or showed a contrast. The moment memories become valuable is difficult to recognize and often few media were created of everyday life experiences. We discuss the implications of these findings for designing systems for creating mementos of everyday life.