Hearing Tests

I am wondering about the accuracy of online hearing tests. As we get older our ability to hear high frequency sounds is supposed to gradually decline. I imagine this is true for the vast majority of people. But my mother was nearly 100 when she passed away and her hearing was so acute that the nurses in the hospital were dumbfounded when my mother recounted the content of a conversation nearly-whispered between two nurses in the next room.

Since I am well into my 60s now I was concerned whether I have lost a significant amount of my hearing capacity. It seems to me that I can still hear the finest nuances from my system but you don't know what you are not hearing. But since I have always protected my ears from loud sounds of any kind I thought that maybe I could dodge the bullet. So, I took 3 online hearing tests and they came out just about smack on with the same results, which I was happy to see. The results said I have excellent hearing.

Here are the links to the 3 tests I used to test my hearing:

http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/

http://www.talkclassical.com/17309-extreme-frequencies-hearing-test.html

http://www.phys.unsw.edu.au/jw/hearing.html

Of course, online tests are not the same as having your hearing tested in a doctor's office. But do they have validity? And, if so, to what extent are they valid? I wish I could find the recent Audiogon thread where someone stated with authority that no one over a certain age (I can't remember the age mentioned) can actually hear above a frequency of 10,000 or 12,000 Hertz (I cannot remember which frequency was quoted).

Do you have any experience with hearing change as we get older and with the validity of hearing tests?