Avoid power sharpeners like the plague . The worst thing that can happen to a knife when sharpened by hand is it will lose its edge. Motor driven wheels and grinders can ruin a knife. The original grinding lines are changed, and the blade can be overheated and loses its temper. Professional grinders use motor driven wheels, but it takes years of practice to get consistently good results.
Most advice concerning knife care seems obvious.
However, there is a lot of abuse going on in today's kitchens. People see in commercials how kitchen knives are abused as hatchets, pry bars, screwdrivers, hacksaws, etc. Do not use a knife for any heavier cutting or chopping than it was designed for. Any guarantee you have will be invalid and you are endangering your limbs. If you need to cut lumber, buy a Ginsu.