I have a Kensington Expert Mouse that's somewhat working but that did not age well. I bought it 3 or 4 years ago. Scrolling wheel never worked properly and completely stopped working after a few months no matter how hard I cleaned everything. Buttons began to decolorate after a year or so and wrist rest support broke apart at about the same time. A huge waste of money.
On the other end, I bought a CST Lasertrack X about 2 years ago and use it extensively 10 hours a day at work. Albeit being a bit pricey, it's been a rock solid solution. Very, very, very good device. No sign of aging or wear or anything. Very low maintenance. Truly built like a tank if not for space exploration! Never missed the extra button. Highly recommend it. In fact I'm getting a second one if the current drop goes well.