Do nuts ever go bad?
Yes, nuts are very fatty, and they will eventually go rancid&mdash; if this is the case, they will taste very poor.  They can also dry out, or in more rare cases (especially if stored improperly) be infested with insects or molds.

Generally, they should be good for six months to a year at their best flavor, depending on the variety (in the shell).

Five years is a little long.  I am not sure I would want to eat nuts that old.