Is there some setting I can adjust to not have to log in over and over in the course of an evening?

Sometimes I will leave the DFF tab and click over to facebook or something...and when I go back to DFF, I have to log-in again. It is especially trying if I click away while I'm in the middle of writing a reply. If I don't save the reply to Word, or at least the clipboard, before re-logging-in, all the beautiful and creative words will be lost.