The odds of hanging on are also iffy. However, magic is experiencing a resurgence of interest thanks to Harry Potter. Children’s party magicians are certainly benefitting from the series. Also, popular television shows starring magicians have made magic cool again. There is still some work to be done to make it cool among the 14+ crowd, but at least they’re trying.
More than anything, if you practice the bejeezus out of your craft and perfect all of your illusions, you will be in higher demand and will be better equipped to hang on. Some people are naturally better at sleight of hand, or patter with the audience, or misdirection (making the audience look one way while you do something sneaky somewhere else), but the more you practice the better you will become, the more seamless your tricks will be, and the longer you should be able to stick around in the business.