There is no time limit in Firefox 4+ versions for the history.<br /> Firefox determines automatically how many pages can be kept without affecting the performance.<br /> You can see the current value via the reads-only pref places.history.expiration.transient_max_pages on the about:config page.<br /> If you still have old prefs like browser.history_expire_days or browser.history_expire_days_min showing on the <b>about:config</b> page then you can reset them via the right-click context menu and they will be removed on the next start of Firefox. See: * http://blog.bonardo.net/2010/01/20/places-got-async-expiration ---- If you lose history then make sure not to use Clear Recent History or use other cleanup software like Cleaner. *https://support.mozilla.org/kb/Clear+Recent+History