Try to set number of days for history setting

Go to Tools>Options. The select Privacy tab. From it, select "Use custom settings for history" from the top drop down list. There you can specify the number of days for retention of history (Check out the attached screen shot )

You can also look at these prefs on the about:config page. http://kb.mozillazine.org/browser.history_expire_days (180) (also affects saved form data) http://kb.mozillazine.org/browser.history_expire_days_min (90)

To open the about:config page, type about:config in the location (address) bar and press the Enter key, just like you type the url of a website to open a website. If you see a warning then you can confirm that you want to access that page.