Odds of Hanging On
Forget about it. If getting in is difficult, hanging on is nearly impossible. Even if you tie your pointe shoes together and use them as a rope to strangle all the competition (again, don't do that), you'll still be out of a job every summer, scrambling to find a temporary gig before the season starts again in the fall.
But let's pretend that you make it big. (You almost certainly won't, but we said to pretend.) The average ballerina today retires at twenty-nine, and that number is falling every year. So what then? Let's hope you have a backup career, because otherwise you'll be moving back in with mom and dad. No matter how great you were at ballet.