Unless you actually stored those values in Session variables, yes, a refresh is all that is needed.
You used "within a session" in your subject, so I'm a little nervous that you read the values from the text file once (say in a login page?) and store them in session variables. If that's the case, then you'd have to have some way of "noticing" the change. But if you mean everything is done via #include's, then you're fine.