Summary: I have had this mouse for over somewhere around 8 years. It has been moved between 4 different computers and 5 different houses. My kids have gotten the ball out and thrown it around/played with it and it still works VERY WELL.
Summary: I bought a used mouse which has a massively sticky ball, worse than my used-every-day-and-rebuilt-twice 8 year old Logitech Trackball. If you have to do anything with precision, this is NOT the mouse to buy. Consider buying an Anker 2000 or 5000 mouse instead.
Summary: I have used this exact mouse for about 10 years, give or take. It has never failed me and I have never had to get a replacement. All my buttons still work, lights functioning, connection is stable, etc. If you have the money, buy this mouse if you want a trackball.
Summary: I have 6 of these. In 2001 I started working at the place I am presently employed. They had this strange trackball mouse (The Microsoft Trackball Optical). I though, my gosh this thing is awful. After a week, I thought I will never have anything else, this thing is just perfect.