Funny enough, I had a similar query.. I would call this a bug in previous versions, in that timeouts were seperated from tomcat's session timeout policy - this can lead to various problems.
 
The good news is, this timeout time you're experiencing is actually tomcat's session timeout.  To increase this, simply look to your web.xml file (under tomcat's conf directory) search for the node "session-timeout"; and update this accordingly in minutes.

From: Uwe Kleinschmidt [mailto:uwe.kleinschmidt@gmail.com]
Sent: 22 February 2007 01:57
To: xwiki-users@objectweb.org
Subject: [xwiki-users] life time of log-in

Gents,

 

I am using BETA 4 and encountered the following problem:

 

Once logged on there seems to be an inactivity period, which forces a log out w/o warning.

The editor for an entry is open, accepts entries but once you want to save what you edited and you took a break of > 10 minutes in between, everything is gone.

 

On the other end with previous betas, I could leave the xwiki for hours go to different URLs, and go back to the Xwiki and I was still logged-on.

 

 

What are the policies here and IMHO both cases described above should not happen.

 

Thanks

 

Uwe