Only current day's history is being saved; how do I reset?
The Help stack does not seem to have an answer to how to reset History to save for more than the current day. I want a much longer period of History saved. How?
Although possibly not related to your problem, I have to remind you that the version of Firefox you are using at the moment has been discontinued and is no longer supported. On top of this, it has known unpatched bugs and security problems. I urge you to update to the latest version of Firefox, for maximum security, stability, performance and usability. You can get it for free, as always, at getfirefox.com.
As for your question, you can either go into Tools > Options > Privacy > Firefox will:Remember history or if you have it set to Use custom settings for history, you can tick Remember my browsing history for at least and you can configure the amount of time it is.
Also, be sure that there's not third party software erasing your Firefox history. Some antivirus/firewalls/security suites/etc. are capable of that.