Welcome to Sleeve Island. I had heard of this phenomenon from other sweater knitters, but I did not experience it on any of the other sweaters I’ve made. Maybe it’s the brioche that’s the problem, but I am definitely getting sleeve fatigue already and I’m not even halfway through the first one. On my previous two knit sweaters, the sleeves felt amazingly fast since they were so much smaller in circumference than the body. I guess for this project, going from the quick little front panels to learning brioche in the round over 50+ stitches made everything feel like it has ground to a halt. If I were smart I’d take a short break from this project, but I want to get it done in time to submit for the KAL I’m participating in so I’m pushing forward for now.