This seemed to have started around FF 31.  I will randomly get booted from my session after being idle for just a few minutes - but more commonly when clearing the cache ( that is - turning on dev mode or using the cache extreme plugin ).  And then other times I will have no issues.  I am accepting cookies from my site - have actually just changed the settings to do so where previously I was not accepting cookies at all.  That has had no effect and just prior to writing this I was signed in for no more than 1 minute, refreshed the page and off to the sign in screen I go.
  I do not have these issues in Opera, Chrome or IE.  Any thoughts?