I'd suggest (untested): backup the cookie file after the cookies that you want to preserve have been written. Then replace the link/entry/shortcut that starts your webbrowser with one that copies the cookies back into it's original place before starting the webbrowser.

You'd probably have to remember to repeat this procedure once in a while, as the formats might change over time.
posted by Joe.Koenig 3 years and 8 months ago Link