Replacement boilers aren't just a necessity, they're an investment.
Time and time again, we are called to boilers less than 5 years old, where poor, inept installation practices have led to very expensive remedial work, to rectify cheap shoddy workmanship.
The longevity of your boiler's lifespan solely depends on the amount of investment in the initial installation.
Obviously, good quality maintenance and servicing will contribute also.
Add to this, manufacturers now becoming extremely fussy (and rightly so) concerning the warranties on these appliances, the installation has to be correct.
Vaillant boilers are probably the most expensive domestic boilers in the UK market. Although not necessarily the best. Bosch Worcester could also be categorised similarly.
There are alternative boilers, some more simplistic and less complex, which are comparable to the most expensive.
IDEAL Logic, Independent, Vogue, and INTERGAS boilers fall into this category, and we have been somewhat impressed with all the models of these manufacturers, and the inclusive warranty periods.