The answer to 'when to replace downspouts' is that you should replace your downspouts when they become damaged, clogged, or no longer effectively divert water away from your home's foundation. Downspouts typically last 10-20 years, but their lifespan can vary depending on the material, climate, and how well they are maintained.
Signs it's time to replace your downspouts include visible cracks, holes, or rust, as well as water pooling around your home's foundation. Clogged downspouts can also cause water damage and should be replaced. If your downspouts are not directing water at least 6 feet away from your home, you should consider replacing them with longer ones.