May i say that i am a service engineer based in Suffolk for a large contractor and i have personally seen data on the Vaillant system showing 0.2% of hoses bursting on the ecoMAX boilers. The Vaillant range i have seen have now changed the design from rubber to copper within copper which is a much better design. Although the issues where the hoses have burst would only occur if chemicals have not been correctly flushed through because they would eat the old rubber hoses from inside until a potential burst took place. Saying that though if you saw the figures ive seen then its a very very small amount of hoses that have actually burst so i wouldnt panic to much about it. Vaillant came out to me in 24 hours and the boiler was as good as new, job done. 
