We have approx. 17,000 miles on our Alenzas and we are still very happy with them. There are many tires out there that start out quiet and progressively get noisier as the miles pile up. Thus far, this has not been the case with the Alenzas.
By the way, Consumer Reports rated the General Grabber HTS as #1 with better than average comfort and road noise. However, unless you hear from someone who's had them for many miles, don't buy them. They could turn out to be excellent tires, it's just that we don't know.
In the same CR list, the Michelin LTX M/S is one of the few highly-rated tires to show long tread life.
The quietest tires are the Coper Discoverer CTS and the Yokohama Geolander. They were also rated in the upper half of the list. The Alenzas showed better than average dry braking, handling, hydroplaning, and snow traction.