If you keep your jar in direct sunlight, over 25-degree temperatures, your honey will start crystallizing and darken in colour (this is when you get the little sugar lumps in your honey). Please note that crystallizing is not a sign of your honey going off
To avoid introducing moisture to your honey, make sure the container has a tight seal and use a dry spoon whenever you dip into a jar. Even a small amount of water can promote fermentation.
Honey has an amazingly long shelf life when stored correctly. Thanks to the high concentration of sugars, honey is one of the most stable natural foods you will find. It can have an almost indefinite shelf life if it's stored properly.