Not sure on how long yet,but you do get logged off if you are inactive for a certain amount.Estimate somewhere between 15 to 20 minutes.
Using the v1.0 style
Now I can not even get to style v1.0 it took me straight to myce beta
The log on area at the upper right is, depending upon how one approaches the page, hidden behind one or another box. That makes it very difficult to access the log in box.