Even if you have taken proper care of your jacket, it still may stop working overtime. If you pull it out of storage after an extended period, you may want to test it to ensure its performance. The last thing you want is to realize it does not work in an emergency situation where you need it. In order to avoid this, you can test it out manually.
To do so, firstly, put your life jacket on and make sure it fits properly and that all zippers, straps, and ties are secured. Then, find a body of water large enough to walk into so your neck touches. From there, lift up your legs and tilt your head back a little. If it does not take any physical effort to stay afloat, then it is functioning properly. If it starts to ride up, though, try securing it tighter to your body (if there are adjustable straps). However, if you still sink with your life jacket on then it is time to look over this list again!