The problem has not been reported to trac, because nobody has yet reported what the problem actually is. A few attempts were made, but once they actually cleared their cookies, the problems went away and those tickets were closed.
Trac is for bug tracking, not for support. If you have a reproducible problem, then trac is the place for it. I have yet to find any problem along these lines that is not fixed by clearing cookies.
Also, your statement about it stopping after a week makes no sense. If the cookie didn’t change, then you’d still be logged in. Also, you still have not described the actual “login problem” you are having as yet.