I turned off the notifications. Didn't need to know every time a cookie blows up.

Firefox lets you do that natively too. Self destructing cookies deletes the cookies after you close the browser tab, not the entire window. If the browser doesn't provide complete isolation between tabs, this'll make it so the cookie isn't there to harvest from. You can set each site to tab/browser/never too.

I use the Perspectives extension for this purpose.