Today I checked my brake fluid just a week after being serviced at local dealer. Most likely they never even pulled the top off the master cylinder reservoir which should checked filled or changed at each service as needed. Needless to say I will have new Dot 4 in both of the reservoirs tomorrow. Just goes to show you if you want something done right you have to do it youself.
I was fortunate to have an independent (a friend of a friend) do my brake bleed for $100 total yesterday. I have 42k miles on my '07. There was plenty of debris in the resevoirs.
In the 09 manual it says do NOT add fluid - the reservior is the right size to match the caliper and therefore you dont need to keep the reservior topped off. As long as it is above the min mark it is fine, and if it is below the min mark either your pads need replacing or you have a leak.