I follow the 12 month rolling. First time in a rolling 12-month, you get the 'advisory' letter; second time you get the 'warning' letter, third time you get the letter that says we're closing/transferring your account unless you give me other instructions.
I've only had to send the third letter twice (and I've closed the account and transferred the funds to their DDA account).
I hear and I forget. I see and I remember. I do and I understand.--Confucius