Components have theoretical maximum ratings printed on their datasheets. However, running a resistor at 100% of its rated power at 80°C ambient is a recipe for disaster. This is where comes in.
Derating Factor = (70) / (130) = 0.538
Open your current design. Calculate the actual power/voltage stress at your max operating temperature. If any component is running above 80% of its datasheet max, upgrade it now. derating calculation
