With Self Serve workflows, there's a danger that a linguist could claim a project to work on, and then abandon it. Unless a superuser or producer intervenes, then that project would effectively be locked to other users.
Claim expiry helps avoid this. Navigate to the Workflow section in Team settings and specify a time period, in days.
After this time has elapsed, captions will be automatically released from a linguist or a reviewer, and made claimable again. To allow translations to be claimed indefinitely, leave blank.