Fortigate Captive Portal Authentication Timeout

Hi Fortinet Community,

I have set up a Fortigate Captive Portal, and I'm having a problem with regards to its Authentication Timeout, already set it to 1440mins. after auth-timeout, my device is force to disconnect, then when reconnecting need to do re-authenticate.

I've read somewhere here, to extend the timeout, instead of idle timeout use hard timeout to extend for at least a month. is there any way to do this with out any timeout?

Thanks...