The answer to 'how often to replace boiler' is that most boilers should be replaced every 15-20 years, depending on the type and usage. Boilers are durable appliances, but they do have a finite lifespan and will eventually need to be replaced as they become less efficient and more prone to breakdowns over time.
The exact lifespan of a boiler can vary based on factors like the quality of the unit, how well it was maintained, and how much it was used. With proper annual maintenance and care, many boilers can last for 15-20 years or even longer. However, once a boiler reaches 15-20 years old, it's generally recommended to start planning for a replacement to avoid unexpected failures or rising repair costs.