Nothing lasts forever. While it's pretty easy to determine the shelf life of, say, Thanksgiving leftovers, it's tougher to know when your seasonal decor has gone bad. Holiday lights, like a lot of things in your home, require maintenance and regular replacement. Do you know the life span of your lights?
Incandescent bulbs should be replaced every 4-6 years.
LED lights last a bit longer, for 7-10 years.
Of course, these numbers are just a guideline. As long as they still function, you can keep your lights for another few years after the replacement window. But be mindful. If you see bare areas on your lights, time to replace them. Loose, wobbly bulbs? Time to replace that string, too. Outdoor lights should be replaced more frequently than indoor lights, being exposed to sometimes harsh winter weather.
And of course, if you feel like your lights are ever looking or feeling unsafe, replace them immediately. It's better to err on the side of caution. Replacing your stock of holiday lights every few years is an expense, but it's a small price to pay to ensure the safety of your home and your family.