Complex sentence: Individuals involved in personal archiving consider all media to be relevant sources as long as this relates to the life, memories and experiences of a person, but a majority of the material is written, photographic, audio or video in nature.
Split into simpler sentences: Individuals involved in personal archiving consider all media to be relevant sources as long as this relates to the life, memories and experiences of a person. The majority of material is written, photographic, audio or video in nature.