Let your PFD drip-dry before stowing. When stowed, make sure and stow in a well-ventilated place. Also, it's a good idea not to leave the jacket on board for a long period of time when the boat isn't in use. Vests function best and last longest when they are stored in dry, cool, dark places.
Never try to speed the drying time of your PFD by placing it on a radiator, heater, or any direct heat source. Not only is this a fire hazard, but it can damage the material and decrease the effectiveness of the piece of equipment, too.
Check your PFD often for rips, tears, holes, and make certain the straps and hardware still function well. There should be no signs of the PFD being water logged, no mildew odor should be present, or visible shrinkage of the buoyant materials. Fabric which shows signs of fading, may be weaker and the jacket should be replaced.
Check your PFD to make certain it is serviceable. This is often required by law, so know the local codes and check your PFD's at the beginning of each boating session to make sure you are within the law.