Unless you go off-roading all year long, chances are if you own an SUV you don't use your four-wheel drive (4WD) during the summer. That's why it's important to make sure everything is working correctly before the winter starts, even if 4WD doesn't take too much maintenance. A functioning system can improve tire traction on snow and ice, decreasing the possibility of getting stuck. 4WD varies depending on the vehicle, so check the owner's manual for the best environment in which to use it and how to engage the system.
Remember, having a 4WD system doesn't mean you can drive figure eights around icy parking lots or drive faster than you normally would in a regular car. 4WD can improve your SUV's traction on snow and ice from a stationary position, but it doesn't make your tires grip the pavement any better when you brake.