Graphics card capacitors
Aluminium electrolytic capacitors are the most vulnerable parts in a PC, where it can get fairly hot. Oli pointed at two different classes of capacitors, where there are two parameters to pay attention to: life in hours, and temperature. A standard electrolytic capacitor is rated at 2000 hours (not much!), and 85°C. Long life caps typically have a 5000 hour life (but note that some types in Oli's second link are also only 3000 or even 2000 hours), and are usually rated for higher temperatures, here 105 °C.

You'll say that it doesn't get that hot inside your PC, but electrolytic capacitors have an interesting property: for every 10 °C lower their life doubles! So a 5000 hours/105°C capacitor will last 20000 hours at 85°C, that's 10 times the life of a standard capacitor.