The critiques I've seen of crunch mode always seem to assume that it's a normal state of affairs, and thus leads inexorably to burnout. We'll have maybe one or two weeks of crunch every quarter or so when we have a major release that everyone needs to coordinate on and no one wants to be blamed for holding up. For those one or two weeks out of twelve, we'll work sixty or maybe seventy hours. It's absolutely effective, and while I've felt tired at the end of it I've never felt burned out. It's also offset by having very relaxed working hours the rest of the time.
I get that some firms see the productivity boost that happens during crunch mode and try to make that the new normal, but is this even that common? Do most firms not do as mine does and just crunch when you need to and have normal hours the rest of the time?