Heated rear screen is a latching switch and will stay on until you turn it off.
Heated front screen switch is non latching, pressing the switch operates the heating elements on a ten minute timer, which will turn itself off either after the time has elapsed, or if you turn off the ignition.
Pressing the switch again will also reset/turn off the heated front screen.
The indicator light for the heated rear screen is in the warning lights on the dash while the indicator light for the heated front screen is on the switch.