Antonyms for the term "more long serving" could include words such as "brief", "short-lived", "temporary", "transient", or "fleeting". These words suggest a lack of duration or continuity in a particular role or position. Alternatives could also include "new", "fresh", "novice", "rookie", or "beginner", indicating a lack of experience and seniority in a given field of work. Ultimately, the opposite of "more long serving" depends on the specific context and the qualities or attributes being emphasized. However, these antonyms suggest a contrast to the idea of longevity, persistent dedication, or established expertise that may be associated with the original phrase.