Across the internet you will see a variety of internal temperatures for beef at each stage of a cook. This is true for conventional methods as well as sous vide. I use 55°C/131°F as my magic number. It is, however, all based on your preferences. Adding a few degrees you will still be in the medium rare range. I have done one at 30 hours and it turned out very good texture wise for thicker cuts. I primarily use this cut for sandwiches where I use an electric slicer for deli thin cuts and for this I cook it for 24 hours.
I normally experiment when I am doing a long cook for the first time. I will divide the meat into 3 pieces and cook at my 55°C setting and try taking a package out at different times. Try 24 hrs for the first one 30 for the second and 36 for the third and see which texture you prefer. I suggest keeping notes in a journal on what you did. It is amazing how easy it is to forget exactly what you did and what you like.