Is there anything I can do to prolong the life of a partially hollowed apple tree?

I little over a year ago we bought a new place near Wichita Kansas that had a lot of mature fruit trees. The trees looks as though they have been neglected over the years. A couple of the Apple trees are hollowed badly, I'm not sure if the damage was caused by rot or insects. I think at least one if not both of the trees is doomed, but they are both still prucing good fruit. When I lived in New Orleans I saw where some Live Oaks were filled with what looked like concrete to help reinforce parts that were damaged by termites. I wonder if I could do something simular to get a little more life out of the apples trees or if it would only hasten there death?