powering on and off

[Kevin Weddle]

When building a circuit from initial design, a lot of components fail prematurely. Is it due to electrically stressing the components temporarily, or powering the circuit on and off? Most commercially bought products are rigorously tested, but I have some simply designed circuits that would probably fail rigorous testing. Are circuits designed around reliability problems like these?

[audioguru]

I have always used name-brand parts. They have max spec's. I design circuits well within the spec's of the parts.

I have designed and assembled hundreds or thousands of circuits and none failed.
I designed some products where tens of thousands were made and sold. Two failed in quality control tests: one with an IC installed backwards and another with a shorted electrolytic capacitor.

[Kevin Weddle]

Designing circuits for reliability is different than designing circuits for performance. But your saying that all it takes is staying within component specification. If I need to power a 100W load, then it's fine to use a device that's rated to deliver 105W?

[audioguru]

But you're saying that all it takes is staying within component specification. If I need to power a 100W load, then it's fine to use a device that's rated to deliver 105W?

No.
Use Name Brand parts and stay Well Within the spec's. To power a 100W load then use a part that is rated to power a 150W load. Then it will probably last forever (but it might cost a little more).