You can check the "Remember Me" box, when you log in, to stay logged in as long as you want. It lets you stay logged in until you click the Log Out button, unless you remove the cookies of your web browser before that.It can also be frustrating that you get logged out so quick.
Also people who use RoboForm can save the login details when the "Remember Me" box is actually checked to make sure it automatically checks the box every time you login using RoboForm.