My question concerns the following Siouxsie and the Banshees lyrics:
Come let's take flight, let's quit this scene tonight
Whilst they sleep on endless, in their wrecked designs
Sleep on endless in your wrecked designs
Is "endless" an adverb in this case? I suspect that this usage is the same as what's discussed in this question, but I want to be sure. Another possibility I considered is that it's an adjective describing the subjects.