Share links don't last forever. They expire on their own, which keeps old links from circulating indefinitely.
The short version
A share link lasts 24 hours. After that it stops working, whether or not it was opened.
The 24 hours is fixed. There's no setting for it, on any plan.
Why it expires
A link that works forever is a link that can be forwarded, screenshotted or found in an old message years later and still hand over your details. Expiry means an old link is simply an old link.
When the link expires, the card it served is deleted too, within the hour — so there's nothing left sitting on the web.
A link can also be claimed into Deeta only once. But until it expires, anyone it reaches can see your card — and, for a Contact Info card, save those details from the web page. That's one more reason the 24 hours matters, and a reason to send each link only to the person you mean.
What the recipient sees
A clear message saying the link isn't available anymore, with no error and no dead end. They'll know to ask you for a new one.
If someone missed it
Just share again. It takes a few seconds and produces a fresh link with a fresh 24 hours.
You can also Re-send from Settings → Shared links while the original is still valid — but note that re-sending sends the same link, so it expires 24 hours after you first sent it, not from the re-send. If the original is close to expiring, send a new share instead.
On Free and Plus, a live link nobody has claimed counts toward your live-card limit until it expires or you revoke it.
Troubleshooting
Someone says my link doesn't work. Most likely expired, or already claimed. Send a new one.
Can I make a link last longer? No — 24 hours applies to every share, on every plan.
I shared yesterday and it's gone from my list. Links leave the list when they're claimed or when they expire. If they accepted it, you'll find them in Who has your profile.
They claimed it — do they lose my details when it expires? No. Once someone has claimed a card, it's saved on their device. Expiry only affects the link.
I re-sent it and it expired sooner than I expected. Re-sending reuses the original link and its original clock. Send a fresh share to reset it.
Questions
Does expiry remove details they already saved? No. Expiry stops the link; it doesn't touch what they've claimed. See Revoking a share for what revoking and taking back can reach.
What if I want to share with several people? Send each of them their own link. A forwarded link can't be added to a second person's Deeta.
Can I check if someone opened it before it expired? Once someone claims a link it leaves Settings → Shared links, and they appear in Who has your profile.
Does expiry stop live updates? No. Expiry is about the invitation. Once someone has accepted a live card, your updates keep reaching them until you stop them. See Who has your profile.