The 24 hour period begins when you first log on. If you first log on at 5:45PM, your 24 hours doesn't end until 5:45pm the following day. If you want more time, you'll have to accept another 24 hours at the same rate.
The service is pretty nice- if you have any trouble or questions when logging on you can dial "56" on the room phone for assistance. They will also provide a network cable if you don't have one.
WiFi is available in the lobby area of selected resorts (convention resorts like BWV, CSR, GF, CR)
Enjoy!