Default [Q] Wake Up Command

Hi everyone!

Just bought Note 3, and I'm loving it.

I have a question... (if it is posted in a wrong place, please forgive me.)

For those who are using wake up command (using S-Voice while screen is off)...
How is your battery life?
Does it suck too much juice because the device keeps listening to its environment?

Thanks a lot in advance!
D3410