Jen, - more time, always more tender. It has been my experience that about 24 hours is long enough for tender results, but what's tender in your chuck roast and in mine may vary considerably. Of course 24 hours longer would have produce more tender results.
However, like most things in life, - it really all depends. There are many cuts of beef that qualify for the appellation "chuck", and they most certainly are not all created equal. I adise you to avoid things like bottom blade and the cuts from the shoulder and get cuts from as close as possible to the rib section. I look for solid whole-muscle pieces that slice and present nicely.
Also, as the names used varies by store and by region, ask the butchers for their advice.
When making a stew, or most often a braise, i will pre-sear the meat, then vacuum package it, then SV cook to enhance flavour development. Try it to get a more tasty outcome. I brown the aromatics in the same pan as i seared the meat to capture all the flavour possible.