You do realize he's talking about a stock exchange? Even a millisecond downtime is unacceptable. Some things don't even need backup, others need testing on identical hardware in identical configuration before deployment. That's just the way it is.
To be fair, it's _unscheduled_ downtime that's not acceptable for a stock exchange. They have scheduled downtimes all the time. For example, as far as I can tell the NYSE is only "up" 9:30am-4pm local time, Monday to Friday, and not on certain holidays.
Now this does mean that you have to make very sure that the upgrade you start at 4pm on Friday will be totally done and bug free by 9:30am on Monday, of course.
And I agree with your larger point that in a situation like that testing done by someone else in a different configuration is of limited (though nonzero) utility.
I understand, and I admit I haven't done anything like that. But isn't it still easier to thoroughly test a day or week's worth of OS changes at a time than to test 6 month's worth or a year's?
