When I was looking for our next (now new) Gas Condenser boiler, Ideal was one of the brands I came across and then dismissed.
Ideal (groupe atlantic) did not compete with say Worcester Bosch – Viessmann etc.
For a Worcester Bosch you could expect 15 – 20 years with no real problems if properly serviced and a little luck.
So 10 -15 years for an Ideal boiler is what I would expect with an annual service before major spares are required.
FWiW; Our Vaillant boiler is also expected to last around 15 years and until recently, Vaillant was having lots of issues (leaks) with the rubber pipework they used inside the boiler, luckily that is now been addressed and Vaillant (hopefully) are back up there with the likes of Worcester-Bosch etc.
A few Gas Safe engineer visits outside of warranty replacing components can soon add up to the cost of a new boiler and nothing worse than the boiler breaking when its cold outside 
Interesting article below on Boiler Reliability
https://heatable.co.uk/boiler-advice/worst-boilers
In a completely sane world, madness is the only freedom (J.G.Ballard).
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