As has been said, just keep checking the setting.
If you want to go behind the Firefox GUI to see the guts of the settings, type about:config into the URL bar and by-pass the dire warning of even going there. Search for Updates and check every bold entry hasn't changed since you last looked at it. Copy every one into a Notepad document so you can go back over them later.
My flash drive Linux Mint which I use for diagnostic purposes is running FF 24 and it works well but it really is best with a trustworthy programme like Firefox, it's best to have the latest version.