.NET自动化服务器的生命周期从Excel中调用

Like the subject says, I wrote a C# class, say Test, then compiled it as a DLL and exposed it to Excel as a COM automation server. Now, you can call the methods of that class in Excel formulas either directly or through a VBA function that itself calls them under the hood. What happens in the second case is relatively transparent (you wrote the code!) while in the first case I assume a Test instance is transparently instantiated and then used (it has to since the exposed methods are not and -- from what I have read -- cannot be static) but exactly when and how is unclear. Thus my question is: what is the precise life cycle of an automation server called in this setting and where is that documented? Like the subject says, I wrote a C# class, say