Hi, the session times out really fast. It is really annoying. I go away for 15 minutes start working again on the wireframe and only when I hit "save" the system tells me that my session expired and that I have to login again. All the work I did with an expired session will get lost.
The current session times out after 24 minutes. Your wireframes are not lost when your session times out. They are stored in the wireframe history. Check out this tutorial to understand the wireframe history feature. http://goo.gl/gN6Gy