I was knitting on the sleeves of Marcus' "Too big for now, in a few years fine" jacket when I decided to measure them. They were 34cm. This is 1cm past where the shaping begins, but the main point is that the eternal sleeves are almost done. Huzzah!
Sleeves are my least favourite part of knitting a jumper/cardigan/anything upper body related. I was taught that a good knitter knits both sleeves at the same time, to get perfect matching tension. It's pretty easy: you simply cast on both sleeves onto the one needle using two balls of yarn and have at it. The only time you can go wrong is if you stop halfway through a row and can't remember which sleeve you were working on, or which way you are going. Don't laugh, this can happen to anyone.
Instead, I've come up with my own solution to such a problem, the ever so humble safety pin. Just pin the two sleeves together in the center and work away, constantly moving the pin upwards as you knit.
Oh, safety pin, is there any knitting dilemma you cannot assist in?