This was 10 years ago when I was in my mid-40's and in good shape, the HRM said my max was 204. Could have been an anomaly, but I had been hitting 190's previously in training using that HRM. I don't really care how accurate it was, since I no longer own an HRM, my only purpose was to explain how I estimated my max.
These days, I just use Lon Haldeman's "one hour a week at 90%" method. I rarely hit that goal, but i try to include at least a few minutes of really high intensity stuff on nearly every ride.