Yes I was aware of the Authentication setting, and it is set to 1 day. I was timed out after something of the order of 10 to 15 minutes during my first use after the V2 upgrade. This was using Firefox 22.214.171.124. Another tab timed out after maybe an hour. Later sessions during that day had not timed out (maybe I was more active!)
When I say I’m being timed out, I click on something (a link to another page, a ‘Save’ button’ or similar) and I get returned to the login dialog. It’s occurred this morning with one tab where I was browsing in Admin>Settings>System.
Is there more than one timeout coming in to play?