I believe the address is valid through June, as stated in an article from theonering.net a while ago:

[i]"The third and final block of shooting started in February 2012, and is expected to be finished sometime in June 2012. However, Peter Jackson has earlier confirmed that some scenes for the second film may be shot sometime during 2013."[/i]

However, I don't know who is still on set and you might get an RTS if the person you write to is gone. I got my Ian McKellen success a couple weeks ago using his agency address in London. He is very good with signing there!

I live in NZ and my mate was an extra. We both believe filming is continuing till Late June. But when an actor is no longer needed for any scenes, they are scene home packing.

Yep. Write to him via his agency. By the way, 'Hobbit' is no longer filming. I got an RTS using the addy. Don't waste your time. :D

you should write to the add in database (london). i received my photo signed and dedicated by him within 14 days. thats very fast, i live in germany. hes really nice and im sure you will get a replay!

Hello! I have seen many Ian McKellen successes to the Hobbit address in New Zealand. My brother is a HUGE lord of the rings and Ian McKellen fan, and I'd like to request an autograph TTM. Anyone know if they are still filming? :D