How long ago was the house built? If it was within the last 5 years, it is probably contruction damage that is causing the problem. If just a few branches are dying, this may be normal. Like any good business, a tree lays off that part of the work force which is inefficient. If the tree is truly dying, it will probably have a lot of little suckers growing off the main limbs and trunks and very few leaves at the ends of branches. Old age for an oak will be 3-500 years old. I don't know what part of the country you are writing from, but I feel that these generalizations will hold true most anywhere.
Bob Underwood, MSU-Bottineau, ND