Going longer at too low a temp isn't going to get you optimal results or increase how much thc will be activated. It's best to go with a shorter time and higher temp for decarb, if you decarb forever, it will effect the taste, it will either dry out so much it tastes almost burnt, or completely disintegrate when you touch it. If you cook the actual butter too long, it will have so much chlorophyll it will taste like grass. I've made butter so many ways, stove top, crock pot, magic butter machine, clarified butter, not clarified, decarbed, not decarbed, lecithin, no lecithin... and all the possible combinations lol. Maybe sous vide is totally different, but I suspect not. The way I do it after so much experimentation is, decarb at 250 for 30 minutes. I have the decarb box for the butter machine, it has a probe thermometer, it says don't start the timer till your inner temp in the box is 230. So I do that. It also says let cool completely, so I do. Before I had the machine I used a Dutch oven w a lid, and let it cool completely before opening. I've done super long simmers on the stove, like 8 to 10 hours and normal times, 1, 2, 4, 6 hours. I've used a crockpot, don't recommend. I've also used various time and temp combos on the magic butter machine. What I've found, is cooking the butter for an extreme amount of time, like longer than 4 hours, doesn't really increase potency in a noticeable way, but it does increase the amount of chlorophyll pulled out and therefore has a negative effect on taste. I've made butter that I literally couldn't cover the taste of. My method now, depending on the recipe, you can't taste it at all. Things that do effect potency, are using lecithin and clarified butter. I use sunflower lecithin, one tablespoon per cup of butter... the lecithin helps bind the THC to the butter so you get every last drop. Clarified butter, (or ghee if you don't want to clarify butter and lose half of what you thought you had lol,) results in a cleaner end result and the butter will be more stable and last twice as long. You really have to just experiment and find how you like to do it, but that's what I've found in the last several years of playing with it.