dik & jorton...
I've been there as well. In fact, I have an entire man-year of 90-hour weeks under my belt: a 7-month stretch, a 4-month stretch, and 4 individual weeks.
The 7-month stretch was back in 1993. I was a principal in a small firm and doing a lot of water system design work. My year was supposed to mostly consist of five design and construction projects, starting with #1 and #2 for one city, then #3 for another city, then #4 and #5 for a third city, all nicely spread out into a reasonable work load. Unfortunately, the first city pushed back projects #1 and #2 because they were having difficulties obtaining some easements that these projects required and the third city pulled forward projects #4 and #5. Then two young PEs, a young EIT, and a cad drafter quit and we had to fire our construction inspector (insubordination and conflict of interest). So, I ended up doing almost all of the design work, some of the drafting work, all of the construction contract administration, and all of the field inspections for all five projects. The rest of the office was also busy (but not as busy as me) because of the staff shrinkage. But, I had the heaviest burden because some of the work involved things nobody else in the company had any experience with. I averaged 13 hr/day, 7 d/wk. The only day I took off during this entire period was Independence Day. Damn near killed me.
The 4-month stretch was back in 2000/2001. I was Assistant PM and Lead Civil Engineer for a 5000-bed state prison in central California. Normally, the Department of Corrections fixes the main elements of the design at the 50% design level and only modest changes are made after that. Unfortunately, on this project major changes kept coming up to the day we signed and stamped the final drawings for bidding. Buildings kept moving and changing sizes, I had to find room in a tight site plan for a yard for charging the electric vehicles that deliver food to the housing units...that sort of thing. The last day changes included moving hundreds of equipment pads for no apparent reason, but I told the client that would have to wait for an addendum. Now, you might think that changes of this magnitude would lead to a schedule extension. But you would be wrong. The state legislature had fixed the deadline and we were stuck with it. Fortunately, we were paid nicely for the extra work and for overtime for the non-exempt employees working on the project. Ten of us (six engineers and four drafters) were on this roller coaster together. The only days during this period that we took off were Christmas and New Years. To make matters worse, the Monday after the Friday submittal for final drawings, two of us engineers and one of the drafters had to get started on a federal prison project that had us working about 80 hr/wk for the next six months or so. Damn near killed me again.
The four individual weeks were less dramatic and, fortunately, were far less stressful.
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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill