Previously the register access checker only inspected permissions and the "status" field ("Enable" checkbox) on registration settings to determine if access to the register page should be allowed - the open and close dates, if any had been specified, were ignored. This could allow the Register tab, for example, to be displayed even if registration was actually closed - an error message would be displayed on the register page in this case. The "set and forget" feature aimed to prevent this by checking for newly opened or closed events during Cron runs, toggling the "status" field appropriately.
In registration:3.4.0, the access checker takes the dates into account, and will remove the Register tab if registration is not open yet or has already closed. Accordingly, the "set and forget" feature has been deprecated since it is no longer needed, see this related change record. For those sites that display the Registration field as a link or form on the host entity page, new options allow a message to be displayed instead of just hiding the link or form, to help with usability.
Sites that continue to use "set and forget" during the deprecation period, or simply prefer having the users reach the register page so they can receive a message, can be configured to use the old behavior. On the global settings page at /admin/structure/registration-settings, a new "Disregard open and close dates in register access check" option is available. This option is automatically enabled for existing installs through an update hook so existing functionality is not changed. Existing installs can then be transitioned to the new access checking at a later time. It is recommended to test the switch to the improved access checker in a staging environment first, to ensure there are no hidden dependencies on the previous behavior for a particular site.
