I don't think I will trust you on that until you have built something, in a fierce global competition, ends up being used by hundreds of millions of people. Perhaps you have?
(I have.)
Again, after that sort of experience I would be glad to discuss this.
A scenario that does actually happen now and then is "the system has gone down, we don't know why, and there'll be hell to pay if we don't find the bug, fix it and get everything back up and running by Monday morning." In that case, fine, work the weekend if you have to - but then take Monday and Tuesday off.