Over time spices can deteriorate and lose their flavor. You can keep spices at their best by keeping them in your freezer. While you may not want to do this for all your spices, it can be especially beneficial for ones that you don’t use very often.
And if you really want to boost the flavor of your spices then buy whole spices rather than pre-ground ones. When you need them, lightly toast them in a frying pan (you’ll know when it is done when you can smell the aroma and spices are warm) then blitz them in a coffee grinder until you’ve reached your desired consistency.