VS 2008 Modifying One List From Several Methods?

I've got several methods that all need to add items to a single list which will eventually be used to populate a listview. I thought about declaring the list at class level so that all of these methods could access it, but it didnt really make sense as the only methods that access this list are Shared methods, so I didnt think it was worth having a list just sat there for the entire time that any instances of the class are created, when in a lot of cases the list would not be used.

So what I ended up doing was just declaring the list in the Shared method that then calls these other methods that need to add to the list, and for each of these methods it calls it passes the list in as an argument. The methods can then add items to the list and as the list is a reference type it updates the underlying list object, so once all of the methods have been called then the list in the calling method is up to date and can be used. Then when that method exits, the list is no longer in scope and so is removed from memory. This all works fine, but it feels a bit... wrong. Would it be better to just declare the list at Class level and not be bothered about the small overhead of the list always being in scope when instances of this class are created that will not even use the list?

EDIT: Actually, thinking about it.. because the methods that use the list are shared then the list would need to be shared as well if it was at class level - so the list would not only be around when instances of the class are created, but all of the time. So it will just be sat in memory for the lifetime of the program wont it? I assume this could make a noticeable impact on memory usage after the list has been filled with data, so I guess if I went down that route then I would have to make sure I cleared the list once I had populated the listview. This is another reason why it just seems much easier and more manageable to declare the list as a local variable in the shared method that then calls the other methods that also add to the list.