In the top menu bar, go to Tools, then Options. Navigate to the privacy tab, and see how many days Firefox stores your history (if at all). You can increase/decrease the number of days it keeps your history.
Also in the Privacy tab, make sure that if the "Make sure to clear my Private Data when I exit Firefox" tab is checked, you click the Settings button next to it and uncheck History (so it won't clear after you exit Firefox)
Also in the Privacy tab, make sure that if the "Make sure to clear my Private Data when I exit Firefox" tab is checked, you click the Settings button next to it and uncheck History (so it won't clear after you exit Firefox)