Even after the reforms of teachers' pensions take effect in September, this will still be the case for retirements on health grounds, though teachers will no longer be able to accept an ill-health pension one day and be back teaching on a short-term contract the next.
This is part of the contract that forms the basis for the patent system: in exchange for teaching the public how to practice the invention, a patent holder is granted a time-limited right to exclude others from doing so.