I frequently leave my A/C adapter plugged into the wall without my laptop. This is because I leave it by my bed, so when my laptop is running low I can just reach down and plug it in without needing to get up and plug the pronged end into the wall. Is this bad for my adapter? I have heard it keeps charging tons of electricity which results in heat that can burn away the wiring after a while. I don't do this all the time, mostly at night when I am working for a few hours. Thoughts on this?
It is not bad for the adapter. However, as with many devices, if you leave the adapter plugged into the wall, even if no laptop is connected, it will still draw a small amount of power from the socket. It's best to unplug the adapter as well if you aren't planning to use it.
You can buy a device called a "Killawatt" that will measure the usage of the adapter and that will really tell you if it's drawing power. Most likely though, the adapter is fine.