Advice required on Integrated Fridge Freezer

Just had my 3 year old Zanussi Integrated FF918/9FFA condemned due to damage to the air duct being damaged by Ice. My questions are

a) is there no way this air duct component can be replaced?

b) is this prevalent with this era of Zanussi product?

c) with fair use what should the life of one of these appliances be?

d) are there other suppliers who do more robust integrated fridge freezers, that either utilise a different cooling approach or more better air duct? if so what should I be looking for?

Any input gratefully received.

Richard