Black knew this fully well, and, in consideration for his colleagues, created a small packet of non-spacetime around his body whenever he started to think about killing himself. As a bonus, he could kill himself as many times as he wanted outside of /Spacetime?, and the /Aether would never notice the difference. This meant that he would not have lost any of his progress upon returning to the space-time continuum.
Like many of the other students, he used his ability for ripping holes in the aether as a way to bypass useless periods of time, and to get a good eight hours worth of /Sleep? instantaneously. He tried not to use this as a substitute for normal bed-based sleep, however, because never in his experience has he been able to /Dream? outside of the aether. Aside from that, he tends to look pretty suspicious going around fully awake after his artificial rest when he'd only been in his bedroom for enough time to perform the /Cantrip?. He didn't know enough about going around spacetime to warp himself out of his house after artificial sleep, at least not without ripping himself into ribbons.
But quite aside from all that, the point is that he was able to hide his manic-depressive disorder from the outside world by using this trick. As somewhat of a bonus, he had also gained some limited planeshifting ability from just watching the planes go by. He had experimented with this for a while, but had recently sworn off because of a particularly horrifying experience that he had had in the form of a /Butterfly. He still doesn't know what would have happened had he actually been caught that one time, but no one will be convincing him to try that plane again any time soon.
Unfortunately for his anxiety, the /Syllabus? that /WinterMoon? had recently handed him said that upon his next visit to the /WikiSchoolOfMagic, he would have to participate in a fairly large planeshifting class. The School was at that time only a slightly organized group of thirty or so well-informed 15-to-20-year-olds, so he wouldn't lose such of the rest of his life by simply not showing up, but he felt some sort of obligation to his friends to come and do this.
Long story short, he showed up. It was kind of a last-minute deal, as he decided to come just soon enough to time-travel there (again, by skipping outside of the aether), but he brought the /WikiGlass and made the class possible. One might say that he made it work, too, depending on your opinion on what makes a (learning) class function.