Just got 8879 IR Speed Remote Control yesterday. Does it have an on/off switch? We don't see one.
No, it doesn't have a specific on-off switch.
But like most remote controls, it uses very little power unless it's actually transmitting. I find that self-discharge in the batteries is more of an issue than the tiny power use testing to see if you're using the controls.
Where this can be a problem is if you throw the controller in with a bunch of loose Lego, and a button ends up pressed. That will drain the batteries quite fast, because the controller is constantly transmitting (just as it would if you used your finger to press the button). So the main thing I worry about is making sure the remotes are all stored with nothing touching the controls.