As of question writing, the record for reuse of a booster on orbital launch attempts is held by Falcon 9 booster B1080, and stands at 14 days. It launched on 2024-11-11 and again on 2024-11-25.

What booster family will hold this record as of the end of 2026?

Launch attempts must be orbital or near-orbital (Starship test flights count as near-orbital). As measured from launch to launch. The second stage must be present but need not be successful. The second flight of the turnaround record need not be successful. The first flight must be successful only to the extent required to attempt reuse.