Forty years ago I was a watchkeeping Radio Officer in the Merchant Navy. My firm never had a set route and consequently trips could be from three days to three months. It always took me about two weeks to settle into the watchkeeping routine (4 hours on, 8 hours off) and only a couple of days in port would mean the whole routine was lost and another two weeks to settle into the pattern again. I was pretty well totally knackered while in the settling in period. How pilots cope so well with the system (system?) they put up with amazes me almost as much as it worries me. things happen a lot slower at sea, and in the end, the ship will usually float on its own while you wake up.