The suspension system is what supports the weight of the car body against the frame. The springs determine the vehicle height and the shocks absorbs the impact from different road conditions allowing you full control while preventing your vehicle from bouncing all over the road. Springs often last the life of the vehicle, however the shocks should be regularly checked for leaks. Weak or leaking shock absorbers will lose its ability to dampen the various road conditions resulting in your car feeling bouncy or even clunking in big potholes. Like your front end, this should be a part of any courtesy inspection and should be inspected in an oil change service.