That just depends on the driving that you do. I lived in Dallas for a while and I went through pads like crazy.....and it was due to the people that drive there.....lots of slamming on the brakes due to the idiots in front of me. Other places I can get a lot better wear from the pads due to easier breaking.
If you are planning on changing them, I recommend getting some Performance Friction pads from Auto Zone. They are a ceramic pad that come with a lifetime warranty. I've got about 30K on mine now and they have never squeaked and arent worn much at all. When they do wear through, I'll take them back!
PS.....make sure to use anti-squeak on the metallic side of the pads!