You can change the expiration date to a future date on the expired invites page, and it will go back to being a pending invite. So you can always grab the link and email it back to the remaining people who have not yet redeemed the invite, or share it via whatever channel is most convenient.
The bulk invite modal doesn’t even offer an expiration date as an option. When you use the Bulk Invite button, the invites are all created individually and it looks like it defaults to one month expiration. You can go to your expired invites page and edit each one individually to change the invitation expiration date. Then you can go back to your pending invites page and select Resend all invites or select one to resend just one invite.