Investing based on the segment's long-term prospects is likely to be very lucrative.I predict that a gold rush in longevity medicines is going to start in the next half-decade or so. That's right: Biotech and pharma companies are going to try developing drugs that can extend human lifespan. And eventually, they're going to succeed, at least somewhat.The early competitors are already getting down to work. Soon enough, there will surely be great opportunities for investment -- as well as a sea of opportunitie ...