This is only for 24 hours, Wi-Fi only, and hotel must provide free internet in lobby/business area (only tested at DoubleTree)
1. Connect to WiFi in free lobby/business area. (SSID=hhonors)
2. Accept Terms and Conditions, check "I want a public IP"
3. Go to your room and connect to same SSID, should be hhonors
4. Enjoy free internet for 24 hours.
You can know to the minute by searching for a cookie from hilton. Search for HSIA. Then look for expiration date--it should be 24 hours later.
Seems they grant 24 hours based on your MAC address, not cookie.