When people enter their senior years, one would hope that they would be more attentive to the Lord and to being faithful to Him--rather than becoming lax in such fidelity. As one draws near to meeting God face to face, one ought to be intent on preparing for that meeting. Our lives, after all, have never been all about us, but all about Him! By the time we reach old age, we ought to have caught on to this. The precious Blood that He shed for us should matter more to us in old age--not less.
Morality doesn't change as we get older. Sexual sin is just as mortal for the elderly as for the young. Nowhere will one find the Church teaching otherwise.
Fr. Vincent Serpa, O.P.