Looking in the VW part bin, we find there is an alternative Heated Rear Window Switch used on emergency service vehicles. I believe this version of the switch may have been fitted to some production Mark IV Golfs in certain markets.
This version of the switch has a built-in timer that automatically turns OFF the Heated Rear Window demister after a ten minute operating period. If the vehicle ignition is turned OFF during the ten minute period, the switch turns OFF fully as well and the timer ceases. You can also cancel the timer operation and turn OFF the Heated Rear Window demister by pressing the switch again at any time.
The standard switch is an ON/OFF switch that stays pushed in when activated. This version has a momentary action and pops back to the rest position immediately, however the normal telltale warning lamp is lit whilst the timer is active to indicate it is operating.
The Heated Rear window Switch on my .:R32 was wired up from the factory to also control the exterior electric mirror demisters, so this switch has the benefit of limiting their operation as well.
This switch may not be the optimum choice if you live in a very cold climate, as ten minutes may not be sufficient to keep the rear window demisted properly. It may require you to keep reactivating the timer to keep the windows clear (instead of just leaving a normal switch in the ON position).
Since I installed this switch I have also converted the exterior mirrors to operate from the mirror switch itself in the door trim, so that I can control their operation separately.