Enabling Lease Time Slate AX (GL-AXT1800)

Is there a way to specify a “lease time” like was available on the Beryl under the Captive Portal app? That app doesn’t appear on the Slate AX I just bought, and I need a way to kick off client connections after about 5 minutes. I’m a bit of a networking noob so sorry if there’s an obvious way to do it in another fashion.

Thanks in advance for the help!