If I run the setup wizard, I can specify my username and password for Github. Right afterwards, if I check Tools > Options > Authentication, I see an entry for my username/host/password. After some amount of time where I leave Sourcetree running in the background, it starts prompting me for my password, and when I check the options, my saved username no longer appears.
This is Sourcetree 1.4.1.0, on Windows 7.
Thanks.