You can set an expiration date and time for a link in the Advanced options when creating or editing a link.
Once the expiration date/time has passed, the link will automatically be disabled. If a visitor visits the disabled link, they are told it has been disabled by the owner and they are shown the owner's name. DocSend does not release your email address on the disabled link screen.
Expiration dates are very useful if you are sending around sensitive or confidential material, or if you want to make sure outdated information isn't accidentally accessed in the future.