Select Not In Other Tables

[FastEddie]

I am trying to come up with a way to determine which of my customers are not coming back in a 3 month time period. For instance I want to know which customers came to my store in January but did not come back in February, March or April.

My query looks like this:

SELECT 
	CustomerID, LastName, FirstName
FROM 
	vJan 
WHERE
	CustomerID NOT IN (Select CustomerId From vFeb) And
	CustomerID NOT IN (Select CustomerId From vMar) And
	CustomerID NOT IN (Select CustomerId From vApr)
	ORDER BY LastName, FirstName

I thought that this is the correct way to write it but I am getting o rows returned and I know for a fact that not every customer who came in January has been back. What am I doing wrong?