I have been using a RB2011 to manage a Hotel WiFi network for the past six months. The only complaint I have had is that a lot of people have to keep re-logging in.
Under “Hotspot Server Profile” I have enabled the cookie option however this only works sometimes. I believe that a lot of browsers may not be accepting cookies or keeping the cookie. I have noticed this with the iPhone. I have to log in every time.
Insure the time on your router is set correctly. The cookie will not work correctly if the time is incorrect. NTP was the answer for me.
If the time is not set, the time in the router defaults to Jan 1 1970, and the cookies it issues will expire in three days, or on Jan 4, 1970. That was a while ago. When the browser session is closed, all expired cookies are dropped, including your login cookie.