Safari Browsing History

How long does Safari on IOS 9.3.2 retain and display it's browsing history for? How can you get Safari to retain and display it's browsing history for as long as possible? Mine currently seems to be deleting a one or two of my eldest history at a time. I was told by Apple that my device would retain and display it's entire Safari browsing history until I physically delete however have since been advised by the that it will only retain and display 30 days.