Yeah it does sound great just not so good for the valve train for extended cruising and since I drive mine quite a bit an extra gear would not only make my engine happier, I wouldnt mine the gas savings either. I live by the strict rule of keeping the rpms under 3k on extended driving which leaves me driving in the slow lane on the highway at about 65 mph. 
It is correct that sustained high rpm is a valve spring killer but here's a surprise...
I spent some time working with NASCAR teams and with CV Products in NC a few years ago. I learned steady speeds are far easier on valve springs than continuous RPM changes. For example, there were more valve spring failures at Michigan than Daytona or Talladega. Longer tracks like Charlotte are easier on them too as the range in speed was somewhat easier. Martinsville (two drag strips with a corner at each end) was absolutely killer! Believe it or not, good synthetic oil carrying the heat off the springs extends life too. Oil spray bars in the valve covers are often used for that.
I have replaced the springs once but attributed that to several hundred drag runs.
It is rare that I get to run more than 65 or 70 for more than a few minutes anyway but it sure sounds good when I do!
