The default drop-down is "forever" in the box. That is typically what people want so they don't have to log in each time. So yeah, every time you log in you have to change that drop-down box if you don't want that. It is logging you out like you wanted, and so each time you log in, you have to tell it what you want again. Once your session times out, everything will reset. It's working like it should unless I'm misunderstanding your question.