Thanks Greg. I have done the testing and confirmed that 'expired lock' doesn't effect others to acquire the locks or the same guy re-acquire the locks. But the expired lock seems misleading the system admin to see whether the user really has locks.
From the testing I found something more interesting.
I used two browsers and two accounts.
Browser A: Firefox with admin account to monitor the lock status (Admin interface)
Browser B: IE with LDAP account to act the lock (Simple edit interface)
I had Browser B access the simple editing interface of an asset's details screen, content screen and metadata screen, then had it back to the front end. In Browser A, I browsed admin interface to check the asset locking status.
In the first checking rotation, details screen, content screen and metadata screen were locked by the LDAP user, expiry time were all ten minutes. I left the Browser A in details screen.[*]In the second checking rotation, details screen, content screen andmetadata screen were locked by the LDAP user, expiry time were eight and half minutes. I left the Browser A in details screen.[*]In the third checking rotation, details screen, content screen andmetadata screen were locked by the LDAP user, however details screen, content screen's expiry time were reset to nine mintues, xxx seconds, but the metadata screen's expiry time went on counting to six minues, xx seconds. I left the Browser A in details screen. [This is weird!!!][*]Then in the fourth and fifth checking rotation, details screen and content screen were reset twice to ten minutes after two minutes, it seemed that Browser B had got the top frame's Refresh Interval work for it, but Browser B was not in either simple editing interface nor admin interface.
The only time the locks will be refreshed automatically is if that top bar is reloading. It definitely sounds like it was there somewhere. Are you sure the top bar was not hidden?