I reset my bike computer every year, so it never goes beyond about 22,000 km (I think that's the highest it's been, but 20,000 km range is pretty typical).

I started off using Avocet computers, but switched to Sigma when the Avocet would reset automatically when in my jersey pocket, especially when it was wet. The Sigmas have been more reliable, but they changed their mounting system in 2003, so I had to get one with the new rotary mount. And since then, I usually buy a new computer from Sigma every couple of years. They make model changes about every three years, and the year is incorporated into the computer name, such as "1009" (2009) or 8.12 (2012).

Had I not reset each year, my fixie that I use for commuting and everything else would have close to 88,000 km on it since November 2009. I should be over 100,000 by the end of October, knock on wood, the five=year mark. Then another three years to reach 160,000 km (100,000 miles).

Luis