I have only one question.  Can it be used forever? Because our brain ans neurotrasmissors/hormones usualy regulate their activity and dossge by how much you alrrady have of a funciont operation. If some brain function is down, the regulation tends to increase the dosage of.substances in the blood that help the process into going to the new normal. If the same function is babove the normal rate for too much time the brain will stop the productions of substabces and even block some synapses to the stimilus. The result is atrophy a hormonal system. If, for example, i inject, constantly, a hormone into the blood flow, the brain will stop its production by itself. This is a form of dependance. 
So, about sleep. I supose this works like a small soporific. Could it be that the constant use make one unnable to fall asleep alone, if he wishes to?
Thats the reason why soporifics dont cure insomnia, because the are paliatives, often prescribed in emergencies or more serious cases where the doctor need the patinte to recover the sleep soon. Insomnia can only be overcomed by your learning and self control, by therapy (it depends on your case, the doctors will always do what they think its best).

Resume: can one use ASMR/binaural beats forever without negative effects on his own sleep metabolism/physiology ?

Obs: follow your dr prescription, if he get you sleep medications, use it. But never use it by yourself, opinion or judgmente before going to a physiciam.
@Paulo Amaral I realize we're getting away from your original question now, but a few things come to mind here...
1) The half-life of caffeine is about 5 hours (though it varies from person to person). So, having a coffee at 16:30 means that half the caffeine may still be in your system by 21:30, then a quarter cup of coffee would still be floating around at 02:30. I personally would have a really tough time sleeping with that going on 🙂
2) The circadian rhythm thrives on regularity! I definitely suggest setting up a repeating routine where your brain will subconsciously know "OK, it's that time of day again, I should start feeling sleepy now."
3) For best results I always recommend NO stimulation 2 hours before bed -- this usually means no screens of any kind. Again, that varies, and if you're using an app like f.lux it'll help reduce blue light. More productive practices may include journaling to empty your brain, some light stretches or yoga.
4) No exercise is also a red flag, though I'm guessing there's a special circumstance currently preventing you from doing any. Definitely want to get back to that as soon as possible -- you're not just a brain in a jar! 😄
I hope you find some of this helpful!
Paulo Amaral