I haven't heard of any Dell specific hardware issues in the last 5 years. Everybody had capacitor problems a while back due to a shoddy Chinese manufacturer. That problem has been cleaned up and vendors are being more careful of their supply chain now.
General rules to extend life -
1) Keep the heatsinks and fans dusted. Use "canned air" to blow out the heatsinks, fans AND power supply with the power off and the unit unplugged. At least once every 6 months, more if you are in a dusty environment liek a factory.
2) Avoid temperature extremes when the unit is On or Off. Don't leave th eunit outside in the cold, bring it in and power it right up. Let it equalize temeprature and any condensation dry out (several hours). Don't set the unit under an air duct or near a heater outlet.
3) Don't overclock, it can reduce life.
4) Try and avoid long (3 months or more) periods of storage.
5) Ground yourself to the case before opening it up and handling components.
6) Don't spill beverges into the computer...
Oh yeah. And enjoy the computer.
