Aging is not a disease, but it's the gradual weakening of the body, as the body gets weaker it gets more prone to diseases. So one doesn't die from aging but from diseases. So if one didn't catch any diseases, would it possible for him/her to live forever? Or just longer than the maximum life span?
No that is not possible ever. There is something called telomere which is present in the chromosomes of cell .These Telomere triggers the action of ageging and leads body towards death. When we are in growing age the amount of telemere is very less but as we get older and older the amount of telemere get increases . The rate of increase of telemere increases with each succesive cell disivision. Hence death is sure no matter what ever you do.
The diseases are only a part of it. Aging is also accidents and such. Cancer would still be prevalent as would accidental deaths. Even a perfect body would eventually fail because individual cell death would lead to organ failure and then death. This cellular death would come from cells failing to commit to apoptosis or from mutations. It won't be possible to live forever, but by using science and medicine, we can greatly lengthen our lives.