Hi StarRiser,
The easiest way to send club invites is to visit a player's profile and click the "Invite To Country Club" link at the top of their profile. Once you've done that the player will receive an email with a link that they must click in order to confirm they wish to join your club. Once the player clicks that link in the email, they become a member of the club.
Club invites cannot expire, only game invites can, so I'm not sure what you mean by that.