I have a custom list template based on the "Calendar" default list template with the "Recurrence" field disabled. In my case, disabled means ShowInNewForm, ShowInDisplayForm, and ShowInEditForm attributes of the Field element in schema.xml are set to FALSE. I had originally tried deleting the recurrence field but the list views expect it to be there so I hid it instead.
The problem is that the user requirements have changed and they now want to enable the Recurrence field.
I have been unable to change the attributes above programmatically. I set the fields and update both the field and the list but the changes don't "take". Updating the schema.xml in the solution and deploying it makes any lists created after that point have the correct setting but existing lists are not affected.
I think perhaps it has something to do with the SEALED attribute?
How can I set the Recurrence ShowInNewForm, ShowInDisplayForm, and ShowInEditForm attributes programmatically?