I am 54, and regularly hit the low to mid 170's when backpacking up hill or when trying to catch bikers that I should never be trying to catch. I asked my doctor about this, and he said that as long as I am not out or breath, feeling no chest pain, not starting to pass out, and can otherwise function normally, heart rate is not that important. What bothers me is when I hit the upper 180's and then stop - stopping makes me feel a bit light headed, but as long as I keep moving I am fine.
My resting HR is in the upper 40's to low 50's depending, (which is pretty cool for an old fat guy!), and my BP is 110/70 on its high days, so I feel less inclned to pay that much attention to heart rate these days. I wear my monitor to track what I do, not when to slow down.