How long to sous vide shoulder lamb chop? How to Sous Vide Lamb says:


  Blade Chop: Medium-Rare: 131°F for 18 to 24 Hours (55.0ºC)
  
  Shoulder:   Medium-Rare: 131°F for 1 to 2 Days (55.0ºC)


Sous Vide Lamb Chops with Chimichurri Compound Butter says:


  132°F for 2 hours


I know sous vide is very forgiving with cooking times, but there is a big difference between 2 hours and 24 hours that can't be accounted for by the 1C° temperature difference.

I would expect at least one of these to be a bad idea, but which one?
Time will determine texture and your target texture is really up to you. Folks typically recommend the “pinch test”. Squeeze the bag and feel it out as you go. Once it’s pasteurized (id refer you to Baldwin for that data) you can shock it and throw it in the fridge and hold until whenever you are serving, so it’s best to start early. 

I haven’t personally processed this particular cut SV, so I don’t have a personal recommendation for you. I recommend keeping a log of every cook you perform with notes about texture so you can refer back to it in subsequent cooks. 

My gut tells me that anything in that listed range will work for you. They will just provide different textures. If you’re looking for tender, go longer.