My next door neighbor is in that situation. She lost her husband to cancer over 20 years ago. Then met a nice guy. He proposed and she got the ring. But they decided not to actually get married when they both discovered what they both would lose if they tied the knot. He is now 88 and very feeble, can not walk, or do much else. She is 80 and healthy and his caregiver. But I think they made the right decision.