That is a tough question. At first I thought no way will I answer that question, but then I thought hey these younger folks need to know the realities of aging and ill health on our sexual lives.
When I was young (teens & 20's) I thought it was all important, more important than how good the rest of the marriage was. I married at 19 and was horny all the time.
Then as I got older (30's & 40's) had kids later in life, it took a back burner but still was there pretty strong but the marriage was still not all that good. But sex kept us going and sticking it out.
Then as I reached 50 all of a sudden I realized it made no difference to me at all. My 55 year old husband had slowed down a bit but still was quite randy at times, but it certainly didn't make up for the unhappiness. All that left was a bad marriage which I promptly left it at 50 years old.
When I married my wonderful current husband our live was blissful in all ways for the first year or so. Then his ill health took away the sexual part but the marriage is so good it has not even provided a bump in the road for us. I love him and truely believe we are soul mates. I would say that sex in marriage can be all important when your young and the passions of hormones run strong. But as age and ill health creep in a good marriage is by far the most important aspect of life. A happy marriage where you love spending time just talking, sharing and laughing together.
As we age men and women slow down. We think about sex and remember the pleasures of it but it is no longer a driving force as it was when we were in our 20's. I know the guys like to say they will be always interested and hot to trot when they are 100 years old, and that is great but they don't know or perhaps understand that their bodies simply won't cooperate with them as good anymore. Thus the little blue pills, and dying with a smile on your face and good woody. LOL LOL