Awesome project! Thanks for sharing!

This sounds like the perfect use case for Wireless Health. This should help you quickly identify the root cause Association, Authentication, DHCP, DNS, etc. It will also help you identify if certain APs are experiencing more issues than others as wel...

Spankym is correct. This can be done via the Guest Ambassador feature, under the Network Wide -> Administration section under Guest Ambassador you can configure the authorized time limit in minutes, hours, days or unlimited.