Smell em. Taste em. There are lots of variables involved. If they still have a fragrant aroma and full flavor then they will be just fine. If you want, throw a few slices of carrot or something in a pan with a little oil and the spice/herb and find out.
If I sold herbs and spices, there is nothing that I would love more than to have you chuck your spice cabinet every 6 months and come see me for more.
Santa Maria 30x20