Order Rules - start and end date & time

Scenario - client want to start a promo at 16:30 adding an item onto an order over £50. Great, dead easy.

Client want to end this promo at 19:30 - pain in the <ahem> as you have to wait around / have to plan your evening around being able to be logged in to turn rule off.

Solution - give us a start date & time field and then an end date and time field which we can set if applicable.

Adding this as a wish while I sit at my desk on a Friday night willing the next 19 minutes to pass swiftly so I can turn off the rule, go home and have a beer.......