There isn't a time limit for the history in current releases. There is only a maximum number of pages that is kept. You may have cleanup software is there is a time limit for the history.

See:

• http://blog.bonardo.net/2010/01/20/places-got-async-expiration

Please note that Firefox 24.0 is an out-dated version of Firefox. We recommend that you update to the latest version of Firefox for the latest in security, privacy and features.

In the current versions of Firefox, the above about:config parameters no longer exist because Firefox no longer deletes history after a certain amount of time. Instead, Firefox will keep as much history as possible and will only start to delete it when it is hindering your browser's performance.

For more information on how to update your Firefox browser, please refer to this Mozilla support article:

• Update Firefox to the latest release