We had some pretty black-and-yellow spiders (Argiope Aurantia) in our yard last fall, and they produced a couple of egg sacs on our house. The sacs are still there, and they look unchanged. Is it possible that they are still occupied, or are they sure to be empty or dead (failed to fertilize?) by now? I did see at least one tiny web in the yard that looked like a writing spider web.
As far as I know, spider egg sacs do not change almost at all when all of its occupants have changed addresses. They are rather firm and mostly hold their shape, they don’t deflate or anything like that. Though slight pressure will likely have a larger impact on an empty sac than a full one.