Destination-wedding invitations go out eight months ahead of the wedding date. Earlier than a local wedding (six weeks out is traditional) because destination guests need that runway to commit travel, book flights at a reasonable rate, and arrange leave. The save-the-date went fourteen months ahead; the formal invitation now does the work of sealing the commitment.
Unlike a local wedding invitation, a destination wedding invitation carries double duty: it is the formal social ask, and it is a practical travel briefing. Build it for both jobs.