I would keep a high condition Model 42, preferably with Cutts or more than one barrel assembly. It is the only gun that I know I could physically handle after all others would be "put away". I'm 61 now and have 81 looking me in the eye. A full choke 42 would be sufficient for preserve pheasants and a lighter choked 42 would be wonderful for skeet, quail, sporting clays, and anything an 81 or 91 year old gun freak would be likely to be able to do. My "user friendly" pigeon club also includes a .410 event every few weeks also, so all bases are covered. Of course, if the choice also included a .410 Parker Skeet or a .410 Purdey, my answer may change.
