According to current thinking, is one 81 mg. aspirin advised over two 81 mg. aspirins to maintain heart health in the "average" healthy person?

One is ok : Risk vs benefits vary for each person. Consult your physician. But, the actual data to prevent heart attack and stroke point toward the use of low dose Aspirin and 81 is enough. Aspirin, as an anti inflammatory agent, seem to have other benefits. A study show that low dose may reduced chances of dying from cancer 20%. American cancer society is not recommending asa as prevention measure, still.