Hotspot portals are based off endpoint groups in endpoint purge policies. If endpointgroupX and wireless mab then permit access
The minimum amount of time is 1 day you can remember an account. This is actually longer than a day because ISE purges only 1x a day. If you register your endpoint to a hotspot (accept an AUP) at 9am day 1 then your device is marked for purge 1 day later. Next day at around 3am (default time out of box) the system will purge your endpoint and you won't get access
Please explain more what you're trying to do and check out this article
How to limit guest access to 1 hour within a 24 hour period
