I have to turn my Apple TV on to make it discoverable by laptops/phones Whenever I want to share my screen to my apple tv, I first need to find the apple tv remote and turn it on.  I used to be able to, at anytime, go to the displays dropdown and select my Apple TV to share to.  Now, my ATV only shows up when I turn it on first.

I see the setting "sleep after X" on my ATV but I don't think this setting is the solution.

Is there a setting I'm missing?

My macbooks and iphone are all running the latest software, and no programs see it at all until I turn it on. ( itunes, beamer, display port, popcorn time )
In my experience, the "sleep after X" is the solution. If I can't see on my apple tv the power diode on - the device is at sleep and I will not be able to use it as a target for airplay. 

It should be said my apple tv is only connected through wifi. I wonder if connecting it through ethernet would make any difference (although I suspect it wouldn't).