even if you leave the lights on accidently by you leaving the switch on ON.... the car has a battery saver feature that cuts power - after about 10 minutes- your headlights go off even in the ON position.
also- on these cars you can set how long you want the lights to stay on after you exit the car. I dont remember what the options are but I think you have the option of headlights being, OFF, on 30 Sec, on 1 min, or 2 min......
this can be set thru the radio.
since you dont have a manual- you can get it online- either thru ebay....... or a free viewable version thru the chevy website.
go here....
https://www.mygmlink.com
and join. enter your vehicle VIN # and stuff, it will tell you if theres any recalls etc... but one of the features is that you can dowload a PDF copy of your manual... here youll find the steps for changing the headlight options along with how loud you want the horn to sound when you arm/disarm etc.