• Invitations made to both LinkedIn members and non-members expire six months after they are sent. This enables LinkedIn to remove previous invitations from the database for email addresses that don't appear to be active on a regular basis.
• email two reminders to the receiver before the invitation expires, letting them know they haven't yet responded. The purpose of sending reminders is to spark the recipient's memory if they failed to notice the original communication.
• The reminders end when a member archives or reacts to the invitation. If an invitation expires, it will no longer appear as a pending invitation in the system. You can then send that same person a new invitation.
• .You can then send that same person a new invitation. You can remove the invitation if you don't want any further reminders to be sent.

Read More: Can you re-send an expired invitation?