An apostille has no expiry date. It certifies that a signature or seal on a document was genuine at the time it was checked, and that does not stop being true.
That is rarely the whole answer, though, because the question people are really asking is whether their document will still be accepted. It often will not, and the reason has nothing to do with the apostille.
What actually expires
- The receiving authority’s recency rule. Many countries require a document issued within the last three or six months, regardless of when it was certified.
- Background checks. Almost universally time-limited, and often the tightest constraint in a visa application.
- Single status affidavits. Usually treated as a snapshot, so most authorities want a recent one.
- Corporate good standing certificates. Typically only accepted while current.
Vital records are the usual exception. A birth certificate records an event that does not change, so an apostille on one generally keeps its usefulness, though some authorities still want a recently issued copy.
The practical test
Do not ask how old the apostille is. Ask the receiving authority how recently the underlying document must have been issued. If your certificate is older than that, you need a fresh copy and a fresh apostille, and no amount of certification rescues the old one.