If you wire them to the vert power they turn off when the car is off. But running around with them on all the time is kind of pointless unless you want to use them as DRLs I guess. Running them at night when there is no need is actually a bad thing because a properly focused beam will be directing your eyes at an optimal distance out in front of the car to see hazards/whatever. Fogs on with the headlights on light up right in front of the car and draw your eyes away from where they should be.
Also fogs should be yellow, as in actual yellow not just normal headlight color for optimal fog/rain penetration and viewing. Too bad all the "JDM" ricers run them in everything but it is actually the proper color and you can find yellow bulbs on high end luxury cars right from the factory these days.
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.