Most clergy I know think of a week when they do 50 hours as an average load; many do much more (though they're probably not married...) I wanted to draw attention to two things I've read recently.
The first is some research (considered here) that suggests there is a significant decline in productivity when excessive hours are worked over the longer term. There can be a short-term increase, but after about six weeks the productivity declines steadily. A 'healthy' load is considered to be around 35 hours for 'knowledge work', which is of course what the 'cleric' does.
The second is some research demonstrating the link between excessive working hours and depression. (Of course, 'depression' is only one of the possible symptoms - a colleague commented that clergy who are overworked and isolated develop 'idiosyncratic behaviours' - I'm sure that's just a euphemism!)
One of the things that I find most challenging is 'switching off', because even if I am offically not working, my brain simply processes all the various issues anyway, and if I don't do it consciously during the day then I wake up in the middle of the night and have to wait for an hour or two for the brain to do its business. There are things that I can do about this, and I'm working on them with the help of my spiritual director - essentially taking time out for contemplative prayer every day, of a substantial length (ie at least half an hour a day, preferably more), and I'm hopeful that that aspect of the challenge can be met.
Here is some advice from - I think - Charles Gore about priestly priorities: 1. Prayer, 2. Recreation 3. Work - because if you put work at #2 then you will never reach #3 and everything will then suffer. Not easy though.