There are so many factors that deal with aging. Cells themselves have a lifespan (They can only multiply a certain amount of times) is probably the easiest to take care of. At least, if you do it right and don't give the person cancer in the process. Though I guess it could happen in 50 years, considering how fast tech is moving nowadays.
I have no idea what I'd do if I lived forever. I wouldn't like it, I bet. I would be so detached from humanity that I would probably kill myself after a while.