I haven't logged in for a very long time as I generally don't logout.
Why would you go to login, if you have already done so ?
I login via my browser firefox at my.avast.com (and don't log out) I then open the avast forum (I have a shortcut to open my profile) and it opens right away, no login required, it has recognised my previous login.
Do you clear cookies, history, etc. etc. when you close your browser (I allow avast to set cookies and don't clear them) ?
I use CookieMonster to manage cookies.