See the question and my original answer on StackOverflow

Well, it depends what you mean by "later". If the underlying UI object is gone (because for example, the user closed the owning application), the pointer may still exist but will be useless and will return error codes if used. It's quite logical, you need to clone all data when you get a hold on it.

Here is a bit of official documentation on this: Receiving Errors for IAccessible Interface Pointers