What is the "active to date" of the latest contact channel used by "Tillman Ernser"?
SELECT max(t2.active_to_date) FROM customers AS t1 JOIN customer_contact_channels AS t2 ON t1.customer_id  =  t2.customer_id WHERE t1.customer_name  =  "Tillman Ernser"
SELECT max(t2.active_to_date) FROM customers AS t1 JOIN customer_contact_channels AS t2 ON t1.customer_id  =  t2.customer_id WHERE t1.customer_name  =  "Tillman Ernser"
[{'max(t2.active_to_date)': '2018-03-23 01:30:52'}]