Yes. Presumably this is what the sleep timer is for, though of course you must remember to set it before you drift off. I imagine you could design a feature where every x_interval you check to see if the user is awake and require a user action to continue playing, but then how do you make it so this isn't annoying during normal use?

Audible is really bad at this. If I set a timer for 15 minutes, and am still awake, I press play (since it pauses). But then it plays without having set a new timer. So to not have it play for hours while I sleep, I then have to take out my phone, look at the bright display, and set a new timer for 15 minutes.

Why cannot pressing play in this instance be like a reverse snooze??

Smart Audiobook Player (Android) has an automatic sleep mode. Also you don't have to press the play button, it indicates the end (fading audio, beep) and you just have to shake/move the device to keep it going, so you don't have to open your eyes at all. It's fantastic.

Does the sleep timer leave a marker for where you set it? Need to double check this, I feel I’ve noticed it before but not consistently enough to know it’s a thing.

At best that still gives you a range to seek through. I'm also not sure if on spotify it saves the location at which I set the sleep timer.