The average lifespan of a boiler is 10-15 years when your boiler is this age we recommend you start looking at replacing it. When you look at getting a new one, make sure you take into account the size of your boiler and the size of your home.
The size is quite important. You need to take into consideration the size of your home and how much water you will need heating. The larger home you have, the larger boiler, you will need. You should also look at the existing space you have allocated for your boiler. Ask yourself, what size boiler will fit in this gap?