It depends on a lot of different factors. If you notice that the caulk is discolored, cracking, peeling, or has gaps - you definitely to replace it. Otherwise, caulk should be inspected every 5 years or so to see if it needs to be replaced. If so, follow the steps below on how to remove old caulking. If you're using a high-quality caulk, as we reference in this post, it should last longer. Also, keep an eye on your energy bills and if you notice they are higher than normal - check for damaged caulk (both interiors and exteriors) that may be letting in or out drafts. At the end of the day, recaulking is something that should only cost you $10 or so and less than an hour so if you're in doubt - best to just recaulk it.