You should consider replacing your boiler if it's over 15 years old, as it may be less efficient and approaching the end of its lifespan. Rising energy bills without a change in usage often indicate that your boiler is losing efficiency. Frequent repairs can also be a sign that maintaining an old boiler is becoming more costly than it's worth. Additionally, if you're experiencing inconsistent heating throughout your home or hearing unusual noises like banging or whistling, your boiler may be struggling to perform. Visible leaks or rust are further signs of serious issues and potential safety risks. If any of these problems sound familiar, it might be time to consider upgrading to a more efficient boiler.