Heart rate measurments are guestimates and the 220-age or the woman's 226-age is one that fits only about 1/3 of the population. Also, a higher max heart rate is not a sign of fitness. The heart rate is what it is, in that it's genetically programmed. However, as one trains to get fitter you'll find the ability to work at higher heart rates without going anaerobic.
Also, it has been shown that the heart rate doesn't necessarily decline as one ages as long as you keep aerobically fit. I use a heart rate monitor when I train and I encourage my clients (I'm a personal trainer and Spinning instructor) to use one as well.
I think if you coorelate your breathing to your heart rate you get a better estimate of your possible heart rate max. That, and also going with highest number seen. You'll know when you get into the "red zone" of your heart rate max when you are thouroughly warmed up and then work increasingly harder until you reach a point that you can no longer increase your effort and at this point most people feel the need to slow down since they are close to puking.
For most of us this is an area we don't care or need to work at. I read an interesting article by Dr. Len Kravitz that illustrates how to determine if you're working at a level that will increase your cardio-respitory fitness:
http://www.drlenkravitz.com/Articles/talktest.html
Vertically challenged, but expanding my horizons.