After all, this couple has been a couple for over 70 years so they must have been doing some things to maintain that relationship. It is common for couples to stop paying attention to the relationship after they are married. By this I mean, they should take time to be together and share in positive common experiences, just like dates. They should give time and relationship issues as much priority as career, exercising, being out with the boys, etc. And they should learn to respect each other's feelings.
Marriage is based on an emotional relationship.
It may have some business characteristics, but, in general, it is emotional. It is not rational. So feelings must be heard and accepted, not criticized or fixed, just understood and accepted. If they practice this, they will have another 70 years.