You can configure the Galaxy tab to automatically disable WiFi under certain circumstances:
- On the Home menu go to > Applications > Settings > WiFi Settings
- Tap on the Menu button > Advanced
- Tap on "Wi-Fi sleep policy"
- You can either choose between:
- When screen turns off (automatically disable Wi-Fi in standby mode)
- Never when plugged in (Wi-Fi will on when device is plugged-in)
- Or simply leave it to default settings (Never)