Grow Old with Me

"Oh, they say that I'm feeble with age, Maggie; my steps are much slower than then. My face is a well written page, Maggie, and time all along was the pen. Oh, they say that we've outlived our time, Maggie, as dated as songs that we've sung, But to me, you're as fair as you were, Maggie, when you and I were young."

- When You and I Were Young, Maggie, as performed by Kilbrannan (original lyrics by George Washington Johnson)

Grow old along with me. The best is yet to be.

This trope is when a romantic couple is depicted going on into their golden years. If mortality or mental illness is a theme, this is a sure recipe for tear jerkers aplenty. Compare December-December Romance, wherein the couple meets in their senior years.

Anime and Manga
""You're right! Without this plain mortal body, I wouldn't be able to pursue my dream! To grow old together. Until our hands will be full of wrinkles.""
 * The ending of Fruits Basket shows 's granddaughter watching them.
 * The Boys Love manga Future Lovers has a dream sequence in its final chapter featuring an elderly Akira and Kento. When Akira wakes up to find he's still young, Kento tells him "I have no intention of dying any time soon. You'll live to be a hundred and I'll be ninety-nine!"
 * In Hetalia, the young French soldier whom France befriends discusses Who Wants to Live Forever? with his wife, and then finishes invoking the trope:

Film

 * Central to the plot of Up
 * Away From Her
 * Bicentennial Man
 * Used as Arc Words in the Christopher Nolan movie Inception...
 * The two main characters of The Notebook live together well into old age.
 * In Don Juan Demarco, the title character helps a therapist & his wife discover the possibilities for passion though their retirement years. Not a bad prospect!

Literature

 * Raymond E. Feist likes to follow his characters and their romantic interests well into their twilight years, which leads to more than a few cases of this trope. See Jimmy the Hand/Duke James' death in The Serpentwar Saga.

Live Action TV

 * A possible version of reality in one episode of Farscape; a Reset Button ensured it didn't happen, at least not the way it's depicted.
 * If you're talking about "The Locket", that wasn't a romantic relationship, though they did grow old together (and it is very strongly implied that they were in love.)
 * On the series finale of Charmed, Piper and Leo travel to the future and meet themselves as an elderly couple. Grandma!Piper even had fresh- baked cookies ready for them in expectation of their meeting.
 * Saturday Night Live ran a skit that poked fun at Jessica Simpson and Nick Lachey when they were married and had a reality show, by showing what things might be like fifty years down the road. In short, Jessica was still a Brainless Beauty, but poor Nick needed to get his eyeballs replaced from rolling them so much over the years.

Music
"While I still appreciate you Let's find love while we may Because I know I'll hate you When you are old and gray"
 * Paul McCartney asks his lover if she'll stay with him in "When I'm Sixty-Four". The Irony that Paul was in the middle of a nasty divorce from Heather Mills when he was 64 was lost on no-one.
 * Ridiculed in "When You're Old And Gray" by Tom Lehrer.

"We've been together now for forty years, And it don't seem a day too much. Oh, there ain't a lady living in the land As I'd swap for my dear old Dutch."
 * The old music-hall song, "My Old Dutch":

"Darling, we are growing old -- Silver threads among the gold Shine upon my brow today; Life is fading fast away; But, my darling, you will be Always young and fair to me,"
 * The old parlor song, "Silver Threads Among the Gold" (beloved of Warner Bros. cartoons):

"Anything for you All of this is true But the best story that I could ever tell Is the one where I am growing old with you."
 * Ludo's song from their latest album, "Anything for You," invokes this:

"I just want to hold you closer than I've ever held anyone before You say you've been twice a wife and you're through with life Oh, but honey, what the hell's it for? After 23 years, you'd think I could find a way to let you know somehow That I want to see your smiling face forty-five years from now."
 * Title of one of the last songs John Lennon ever wrote. Sadly averted.
 * Journey's song "After All these Years" is sung from the point of view of a fellow who is Happily Married and utterly delighted that he's had the chance to have a long life alongside his wife.
 * The premise of Stan Rogers' "Forty-Five Years" from his debut album, "Fogarty's Cove".

Newspaper Comics

 * The Pattersons in the epilogue to For Better or For Worse

Poetry
"Old Darby, with Joan by his side You've often regarded with wonder. He's dropsical, she is sore-eyed Yet they're ever uneasy asunder."
 * Darby and Joan, from a poem by Henry Woodfall published in 1735.

"Grow old along with me! The best is yet to be, The last of life, for which the first was made: Our times are in His hand Who saith, "A whole I plann'd, Youth shows but half; trust God: see all nor be afraid!""
 * Trope Namer is the Robert Browning poem "Rabbi Ben Ezra:"

"John Anderson, my jo, John, When we were first acquent, Your locks were like the raven, Your bonnie brow was brent; But now your brow is beld, John, Your locks are like the snow; But blessings on your frosty pow, John Anderson, my jo!"
 * Robert Burns's "John Anderson":

Webcomics

 * "Together"