Is it possible to make a notification automatically disappear after a period of time?
You can use the AlarmManager. I think is more appropriate and more easier to implement than an Android Service.
With AlarmManager you do not need worry about make something running until the time finish. Android do that for you, and send a brodcast when it happen. Your application must have a Receiver to get the correct intent.
AlarmManager
Look theses examples:
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