Button Up for Medicare Advantage During AEP or T65

For both AEP and T65 the name of the game is keeping the business you wrote at the beginning of the period for both situations.
How do you button-up your business after you leave so that an agent doesn't come in at the end and swoop it up? Do you mail reminders or letters to them afterwords summing up their plan and stapling down any future doorknockers/callers?
Appreciate any insight into how you keep your business on the books for those that do these two categories. Thank you,

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