In general, standard boilers last between 10 and 15 years in a usable state with minimal maintenance, although sometimes they can last 20 years. However, beyond that, it's worth updating. CEE recommends replacing a boiler when you are 25 years of age or older. A boiler can operate beyond this age, but it will operate less efficiently and is more likely to need more frequent repairs as it ages.
This means that you'll pay more to heat your home as your boiler ages. Technically known as electric shock, it will remove dirt buildup and must be done when a new replacement boiler is installed. A reasonable alternative to replacing the boiler is to buy new boiler doors and seal them hermetically, then clean the boiler room and install additional lighting. Therefore, any central heating system that uses a boiler that is more than 20 years old is likely to be significantly cheaper by replacing it with a condensing boiler.
Older boilers, due to their inefficiency, will generate higher heating bills in the home compared to replacing a modern boiler. In the case of a steel boiler, the boiler and its controls and the burner are generally removed and replaced when the boiler is replaced, since it is economical and some codes prohibit the installation of used parts. My advice is that the 10 years to replace the boiler isn't too bad, because the better it is (Vaillant and Worcester), maybe you can delay it a bit. Periodically replacing anodes can extend the life of a water heater or boiler, although new boilers are often not equipped with anodes.
When a manufacturer stops making a certain boiler model, they may continue to manufacture replacement parts for a few years, but will eventually stop when the number of boilers is too low to be worth it. When considering repairing or replacing a boiler, first assess the condition of the metal from which the boiler is made, by any available means. The labor cost associated with replacing all sections is sometimes only slightly higher than the cost of replacing one section, since other sections generally need to be dismantled to remove the leaking section. It may be something you can fix yourself, but it could mean that your boiler needs maintenance, repair, or replacement.
Unfortunately, all sections are damaged by feed water at approximately the same rate, so it can be argued in favor of replacing all sections when one leaks. Similarly, if some sections of a cast iron boiler have been replaced, it is reasonable to assume that the other sections will need to be replaced soon. This combination of old and old technology means that an older boiler is likely to have significantly higher annual operating costs, compared to a modern replacement, up to 300 pounds sterling per year in a typical townhouse. As mentioned, the condition of the metal from which the boiler is made is a primary consideration for boiler repair or replacement.
Unfortunately, few boilers receive treatment for new doors or cleaning covers, and many boilers are replaced when flue gas leaks worsen.