We leave the hallway light on in case one of the kids wakes up and needs to use the bathroom. It's a low wattage globe and much easier than having to be woken up to turn the light on so they can find their way.
No, we turn all the lights off when we go to bed. The only exception is when my grandparents come to visit. On those occasions we leave the landing light on so they can see where they are going if they need to go to the bathroom. Once my nana fell down the stairs during the night on a stay with us, so we now make sure that light is left on.
No way - if I need a light in the middle of the night, I reach for my phone by my bed, or fumble around until I find the main switch. The occasional bump to the shin is worth the saving in electricity!
This is weird at my age . . . . having always preferred a nice dark room for sleeping, I have, over the last year or so used a night light. This is because I have had a few really horrific nightmares where I couldn't even move, let alone get to the bedside light. I have a subtle blue night light in my ensuite, so it is not too intrusive but it really helps if I get the heebie jeebies. This period is also when I fell in love with my iPod for talking books - very soothing at night :-)
No, we never leave a light on, just for the 2 of us. The hall light turns its self on, when 1 enters the hallway. I don't like wandering around during the night, as I like to sleep, but when I wake up to use the loo, I turn on my bedside light, & then go & fetch my laptop from another room, & the hall sensor light comes on, so I'm not stumbling about in the dark.