Question: Renaming windows forms?

I'm working on resolving an issue, and the way that we decide depends upon the prevalence
of a specific scenario. I'd like to know your opinion on the following Windows Forms
scenario.

How often do you rename the form class without renaming the file that holds the form
class? ie how often do you change "class EmployeeForm" to "class AddressForm" without
also renaming the form file?

Thanks