I am an estate auditor by profession. It is very likely that Britney will stay under a conservatorship for the rest of her life, unless her condition improves long enough to show that she is not a danger to herself. She likely also has a guardian of her person. It is unusual for an adult ward to have a conservator but not a guardian.

Conservatorship is not a prison. The conservator just safeguards her against reckless endangerment of her estate for her own sake and for the sake of her children. In addition, conservators are almost always bonded, and conservatorships are audited by the court, so the conservator does not have cart blanche to abuse the assets in an estate.