You're under 18.

If you avoid cigarettes, meth and drunk drivers you should be able to live damn near forever, unless we completely f* up and lose our drive or our ability to continue to advance technologically. By the time you're in your late 30s or early 40s you'll have a much better idea. If you're still typing on the Internets (in whatever form it is 20 years from now) you'll be able to make a MUCH better informed decision. If you're sleeping in a rough shelter and hunting/gathering for food with what's left of civilization, well the cryonics wouldn't have helped anyway (the corpsicles will have been thawed and eaten with the rest of the stored food).