You have full control over how and when your proposal is seen by your recipients. That includes setting an automatic expiration date for the proposal to become inactive once that date has come and gone.
You can set, reset, or remove an expiration date by clicking the Schedule icon inside of the proposal builder.
Your proposal will expire at midnight on the date indicated. In the example above, this proposal will become inaccessible at 12:00AM on 3/31/2018. Once the proposal expires, any notification links that was previously sent to recipients will no longer be accessible. Don't worry, if you wish to modify your expiration date to some point in the future, this action will reactivate those links automatically. You don't need to send new notification emails.