Let's put it this way:
If you don't skip scenes, if you actually take the time to read and understand. It will take over 50 hours to do it all. If you pause to enjoy the sex scenes, you know, to free your dominant hand, well, get some lotion or you'll have friction burns.
But, I know that enjoyment of a game goes further than time spent playing, so, prepare to have a few characters living rent free in your head. If you have a bit of a funny bone in you, make sure you can laugh out loud without problems, drinking coffee while playing, may not be a good idea.
I would recommend making breaks every 5 hours or so, go out, see the family, notice how much the kids have grown before coming back...
Peace