Created attachment 555088 [details]
Since update =sys-auth/pambase-20150213-r2 was introduced, automatic unlocking of gnome-keyring storage doesn't work anymore.
gnome-base/gnome-keyring is version 3.28.2.
- lightdm (stable)
- xfce (stable)
Downgrading pambase to a previous stable resolves the problem.
Support for gnome-keyring should be added to lightdm package. See bug 652194 for more info.
Test again, it must work now for a long time.