How long should wheel bearings last?

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On 12/5/12 at 44,787 miles all four of the wheel bearings were replaced at Land Rover of San Antonio, part of the Cavender auto group. I heard a roaring noise and they found all four hub bearing assemblies needed to be replaced. The cost was $2,231.62 . I appealed to them that my wife drives this car, to and from work,then to the stores. I called the parent company and they paid $1,000.00 of my bill. On 12/20/13 at 61,100 miles I drove my wife's car and heard the rear end making noise again. I thought perhaps it was the tires I purchased at Sears. The tires were good but they had two mechanics confirm it was the rear bearings. I went directly to Land Rover of San Antonio and they said they only warranty the work for one year and that I am 15 days over. I told them they are either useing defective parts or do not know what they are doing. They also told me to go and call Land Rover of America myself and see if they will help. Also last week, while closing the sunroof the right guide bar fell off . The cost of repair, $565.00 My 53 year old wife only drives to and from work on the interstate and to the stores. This car has never been off the pavement. My question, how long should sealed wheel bearings last?