If it was designed to be turned off, they'd have incorporated a power button/switch. My Time Capsule's on all the time, and that thing gets even hotter than the AEBS cuz of the hard drive in that sucker. Don't worry about it.
Also, if you want you could always raise the AEBS off the surface it rests on with some plastic risers. This creates airflow beneath it and helps with cooling it down. My TC runs a lot cooler since I've done that.