If I had this confidence, I'd put in the hours cheerfully; I've had spells of 80-100 hour weeks in the past and invariably it was caused by sales people or managers over-promising without asking a technical expert, and could have easily been avoided. Doing the hours resulted in some vague gratitude at best.
Now (in a new role), I can see clear evidence of things which are correlated with promotion, but working long hours is not one of them.
