I've noticed on my iPhone 6s since ios 11.4 airplay no longer stays connected to a device. Since ios 11 I think Apple had set airplay so once connected you had to manually disconnect which I found very helpful. Now it seems to timeout again after about 5 minutes. as anyone else noticed this or have I picked up a bug somehow. It is very annoying if Apple have changed this back. You should at least have a setting to choose if you want to stay connected or not.