DO AS I SAY NOT AS I DO most guys in the trade never service their own boilers as is so often said in the CC
To be fair most guys not in the trade cannot nip out and fix the boiler when it stops, glance at the thing for known issues to see if they're a problem or replace a finished boiler with a reclaimed model won from a job with an unnecessary replacement or an upgrade.
Also if they put it in themselves many of the issues that stop a boiler prematurely will have been dealt with as it was installed correctly and not to satisfy a customers desire for the cheapest quote.
Customers know the cost of everything but not the value.