I just had a look in the password file and found ...
So it appears that the <last_logout> tag is not being updated.
Some activity from the messages file ...
18-Oct-2013 15:52:12 [2003883@10.11.112.178] {ops} LOGOUT
21-Oct-2013 06:40:03 [10.17.48.165] {ops} LOGIN user "2003883" (attempt)
21-Oct-2013 06:40:04 [10.17.48.165] {ops} LOGIN user "2003883" (success)
22-Oct-2013 07:01:51 [10.17.48.176] {ops} LOGIN user "2003883" (attempt)
22-Oct-2013 07:01:51 [10.17.48.176] {ops} LOGIN user "2003883" (success)
22-Oct-2013 07:10:13 [2003883@10.17.48.176] {ops} LOGOUT
22-Oct-2013 13:26:32 [10.17.48.176] {ops} LOGIN user "2003883" (attempt)
22-Oct-2013 13:26:32 [10.17.48.176] {ops} LOGIN user "2003883" (success)
22-Oct-2013 14:13:16 [2003883@10.17.48.165] {ops} LOGOUT
23-Oct-2013 06:24:30 [10.17.48.165] {ops} LOGIN user "2003883" (attempt)
23-Oct-2013 06:24:30 [10.17.48.165] {ops} LOGIN user "2003883" (success)
25-Oct-2013 22:25:42 [10.17.48.90] {ops} LOGIN user "2003883" (attempt)
25-Oct-2013 22:25:42 [10.17.48.90] {ops} LOGIN user "2003883" (success)
25-Oct-2013 22:43:45 [2003883@10.17.48.90] {ops} LOGOUT
Mark.