Document and Media Library document checkout never times out. The file will remained locked until the user who locked the file unlocks it.
The following properties were added to portal.properties:
This property sets what happens with a checked out file when the lock expires.
Expected values are 0 for cancel checkout (default) and 1 for auto check-in.
This property adds a listener for a specific class by setting the property "lock.listeners" with a comma-delimited list of classes implementing com.liferay.portal.kernel.lock.LockListener.
Document and Media Library file locks were set by default to never expire with the following setting in portal.properties:
This has been changed. Now, the lock by default expires after 1 day.