Frugality and food safety are sometimes at odds, especially when your grocery budget tightens up. It's obvious when something such as milk goes bad, but it's harder to tell with bacon. It often looks and smells just fine, even after the date on the package. If it was frozen and later thawed, the freshness date becomes an even less reliable a guide. Fortunately, frozen bacon remains edible almost indefinitely.
Traditionally, bacon was hung as a dry slab in the butcher's shop and sliced to order. Modern commercially packaged bacon contains a lot more moisture, and it's much more perishable. Most manufacturers and retailers use a system of "best before" dates to make it easy to monitor the bacon's freshness.
The sale date printed on the package is a freshness date. The bacon should be consumed on or before that date, to ensure the best possible freshness and flavor. After that date, the bacon doesn't magically become inedible, it simply begins to lose flavor. Once it's opened, it should be eaten within seven days or it may begin to spoil. Usually its color will fade to gray, and it might develop a sour smell or off flavor.
If you eat bacon only occasionally, or if you've taken advantage of a remarkably good sale price to stock up on packaged bacon, that "best before" date can become an issue. The simplest solution to the problem is to freeze the bacon, either in its original packaging or separated into smaller portions in freezer bags. The USDA recommends using frozen bacon within four months, but that's for reasons of quality. Over longer storage times, the bacon might absorb odors from the freezer or become freezer burnt. As long as the bacon looks and smells fresh, it's perfectly good to eat even after extended freezing.
Freezing vs. Expiration
Freezing stops the clock on your bacon's "use by" date, so that freshness date on the package can be ignored once it's frozen. A more pertinent piece of information is how close the bacon was to that best-by date when it was frozen. The USDA recommends eating bacon within a week of its freshness date, so if it was frozen at the last possible day it should be eaten within seven days of thawing. If you froze the bacon well in advance of its freshness date, you don't have that time constraint.