Replacing your old boiler is no guarantee of more reliable service � according to a friend, who repairs boilers.
A new boiler would almost certainly be a �condensing� boiler; my friend advises that in order to achieve improved efficiency, the heat exchanger of these boilers is made from a much thinner gauge material. The result of this is that the life expectancy of the heat exchanger is very much reduced (my friend reckons most won�t last more than 3 years). And at over �400 to replace (the heat exchanger) � you would be better off trying to maximize the life of your old boiler, before it really does need replacing.