Heart rate training and age

I am a 58 year old male, 6' 2" 220 lbs. in good health with no history of heart trouble. I exercise regularly with resistance, steady state cardio (swimming, jogging) and I teach scuba diving.
I have had a stress test on the treadmill with ultrasound and a radio isotope test as well. I was given a completely clean bill of health
I own a Polar heart rate monitor. Using the usual formulas, my theoretical max heart rate is 162. 80% of that is 129. At 129 bpm I am loafing. I can get my heart up to 160 bpm with no pain although I'm working very hard and cannot sustain that rate for very long. I get my heart up to 150 bpm and then usually back off until it's in the upper 120's and then go again. I feel fine. My question is: am I endangering myself if I get my heart rate up in the 160 range? I feel no ill effects afterwards, I have no pain or shortness of breath, no pain in arm, back, chest, throat, I simply feel that I have worked out hard, well and thoroughly.
Sincerely Yours,
Stephen Mendel

[CCF HeartMD6]

Achieving and maintaining a MHR of 60-80% for 20-30 minutes is considered by most standards, a healthy cardiovascular exercise routine. For high endurance training, there should (theoretically) not be any problems of achieving a heart rate that is higher in the absence of any symptoms, especially if you are only maintaining it for only a limited period of time.