Like most Electronics made today I expect them to last 5 years. If you get a few more out of then you are doing well. I have had a number lose their screens and a few toggle switch failure. All my really old ones have failed. I have also had a number of participants complain of screen going, this seems to be the biggest failure point.

My GPS's get used in Wilderness Navigation classes and I use them a lot in the bush so they may get a little rougher work then most GPS Receivers. I do not replace them until they start to fail, but nearly every year I buy a new one and put the older one into my class box for participants to use. This means that now I am rarely using one more than two years old.