I got an answer from a Fire Fox Forum and am posting it here for others that may want to use the auto fill in feature when surfing.
Details like websites remembering you (log you in automatically) are stored in a cookie.
So you now appear to keep the cookies from those websites.
This should have nothing to do with the places.sqlite file.
Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
- Tools > Options > Privacy > Cookies: Exceptions
In case you are using "Clear history when Firefox closes":
- do not clear the Cookies
- do not clear the Site Preferences
Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, passwords, and other website specific data.
Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you would like to keep.