Spices do get old and they lose potency and complex layers of flavor. They have a shelf life of between 1 year and 5 years depending on the type of spices. When their shelf life is over, they need to be replaced with new ones. Go to http://www.mccormickgourmet.com/Products/LifeofSpice.aspx for details.
yes they do and they will change color. average shelf life after opening is 6 months.some last longer. garlic powder can turn rancid quickly. spices are best stored in a cool dark place. i buy them in bulk sharing them with my family...thus saving money .