The session timeout of WebOffice 10 R3 is by default 30 minutes. You may change this value in
<WebOffice application path>WEB-INF\web_user.xml

Session timeout in web_user.xml
Note: The Life time of session objects should be the same than the session timeout in the web_user.xml.
Note that the Application Server will need more memory if you increase session timeout because inactive sessions will stay in memory longer.