Time is definitely an issue with SV. You can work around it by cooking strategically, sure, but sometimes you just have to cook something more quickly than lower temps allow. I am a big proponent of cooking in batches at low temps for long times and freezing the surplus, but I only buy corned beef once a year and I don't have unlimited freezer space, so my stores are usually depleted sometime in the fall. This time, I was in a time crunch to make a Reuben kit/gift-bag for a family member who was returning home after a long hospital stay, and I'd already eaten all my frozen 48/140F corned beef from last year. Even the best True Students of SV sometimes need something cooked right-the-****-now. This was one of those times.
As for the moisture loss and acceptability, I honestly don't think it mattered for the way that I was preparing it. I slice my corned beef across the grain as thinly as is possible without the use of a deli slicer. If you're going to eat big hunks of corned beef and cabbage, or for some reason like really thick slices on the sandwich, it's probably worth it to go the extra time. But if you like it thinly sliced? And are going to be slathering it with Russian dressing, kraut, and melted cheese? I don't think that the extra time makes for a better product. I'm not even sure it makes for an appreciably different product by the time it's on the plate; my Reuben was as delicious as it always is (and I've always gone 48/140 previously). Of course, I didn't do the Pepsi Challenge and compare them side by side. But the meat was tender and not-at-all-dry. You could have piled it twice as high and still bitten cleanly through it without a struggle (except, perhaps, for the initial discomfort of unhinging your jaw). Even though the brisket was cut from the flat, it was nevertheless on point. Way beyond acceptable. 10/10, would make again.
