EEA family permit valid for 4+ years

My wife happily received her passport back from the British embassy in Beijing today with an EEA family permit stuck inside. We were surprised to find that the "valid until" date of the permit is the same as the expiry date of the passport -- in 2010. The UKvisas website indicates that family permits should only be valid for 6 months.

Any ideas whether this is a policy change or just a mistake by the ECO? Even if it's a mistake, I presume it still stands. So, is there any point applying for a residence document when we arrive?