The steps to display offer expiration dates depend on which version of Make an Offer you are using.
Latest Version (V2+):
To show customers when their offer will expire:
In the app, click the Rules link in the navigation menu.
Click on an rule, or create a new one.
Under the Expires when accepted section, select an expiration date.
Click Save.
This will display the expiration date for the offer to your customers.
Legacy Version (V1):
To set when accepted offers will expire:
In the Make an Offer admin section, click Setup.
Go to the Incentive Configuration tab.
Under the heading C. Select expiration of your offers, use the drop-down menu to set a time limit for expiring offers.
When this time limit passes, the checkout link for accepted offers will no longer work for customers.