It's appalling that anybody thinks 8 years is a good or acceptable lifespan for a new rad of any construction, are You F'ing kidding? I have 50+ yr old rads that aren't leaking yet. 15-20yrs with reg maint. or lifetime coolant should be expected.
Its not like its gone bad! Kind of hard to say how long they last until they break, but I have a plastic tank radiator in my truck that's 18 years old too.
