In almost all circumstances, yes. Roughly 50% of the equipment that comes across my workbench (mostly fairly delicate medical instrumentation, some audio equipment) has failed due to dodgy soldering at the factory. I have *never* had a repair bounce because of my soldering. Actual component failures are rare, except where the equipment has been severely abused.
How do you know he's risking the life of *anyone*? Perhaps he wants a fire alarm panel for his garden shed, or something.
I would be deeply unhappy about an alarm "engineer" who was not familiar with the equipment right down to component level coming anywhere near my house ;-)
If you're content to be a part-swapper, that's fine. Just don't call yourself an engineer.
Gordon