With ATL v3.0, it is not recommended that you reuse host windows. To ensure the robustness of your code, you should tie the lifetime of your host window to the lifetime of a single control.
For information on creating controls, see How Do I Create A Control Instance?
For information on destroying controls, see How Do I Destroy A Control?
Note A future version of ATL will allow host windows to be safely reused with simple calls to the CAxWindow::CreateControl or CAxWindow::CreateControlEx methods. Unfortunately, calling the current implementation of these methods will result in leaks.