The chances are if your email marketing list is more than six months old, at least some of the contacts will have changed jobs, moved to a different point in the buying cycle, or forgotten why they signed up to hear from you in the first place.  

So it pays to re-engage. Grow, nurture and prune. Balance quantity and quality. As this post from B2B Marketing shows, a small but well-engaged list of email subscribers is much more valuable than a large list of disengaged or dormant contacts.