Nevermind, of course the Insert method replaces an existing item with the same key while the Add method only caches the item if there isn't already an item with the same key.

But will Insert cause a purge of dependent items, like if I did a remove followed by Add, or is the insert method there to avoid this? I'm looking for a way to cache an item without expiration, but upon a certain event I want to change the expiration for that item so that it (and items dependent on it) expires in a few minutes (rather than expiring it right away by using remove). Can this be done?