There's more to it than that. Statistical analysis and semiconductors combined in the 80s to reduce such testing. Back in the mid 80s we were still testing every unit in an oven before shipping it. Deming's work in Japan finally was being recognized here in the US and, since then, businesses have sort of "devolved" his theories into formula for increasing profit. Things just don't get tested as much any more and, overall, they're still pretty amazingly reliable.
This is why, when I buy a high ticket item like a new monitor I run it 24/7 the first month or two. For monitors, I have a series of high contrast pngs that I will cycle, with the brightness and contrast maximized, for hours while I'm away. That way, if the thing is gonna die, hopefully it will die before the 90 days or whatever runs out.