Below are two 'optional extras' which will prolong the life of your boiler.

Magnetic Filter
Over time rust will inevitably form on the inside of radiators
and cause black sludge to circulate around your heating system
and into your boiler. Fortunately the sludge consists mainly of
iron and can be removed using a magnetic filter. These cost £120
to fit and will prolong the life of your boiler.

Shock Arrestor.
Cold water is supplied to homes at a constant pressure but valves
opening and closing (most commonly in washing machines) can
cause a surge in pressure which can damage boiler components.
Fitting a shock arrestor costs £50 and will absorb any potentially
boiler-damaging spikes in pressure.