1. Are you referring to self-registered guests? If so, you need to edit (or change) the value of the field in the guest_register form. There is a default field called expire_after. The default value of this field is 24 hours. You can either change this value or create a new field and substitute your new field for thie expire_after field in teh guest_register form.
2. To clarify your question. Do you want the device to have to wait 24 hours before being able to get back on? Or are you looking to set it so it caches the devices for 24 hours before it makes them re-register?