99% is just a spy balloon. These have been used for decades. They haven't shot it down because they want to observer its capabilities. How long can it stay up?

99% is just a spy balloon. These have been used for decades. They haven't shot it down because they want to observer its capabilities. How long can it stay up? What's its maneuverability? What are they are interested in looking at? How is it communicating back home? In war its very useful to observe the enemies capabilities, especially before escalation.