At the same time, however, this is a double edged sword, and it does very much so swing both ways. In this case, we also have the issue that a longer lifespan, leaves more time TO learn... consider if da vinci existed today, with the total culmination of all information up to this point, whot could he do with it? The capacity to see new information and correlate it to older information is important, as is the differing perspectives... by always changing to a new generation, we also deprive ourselves of older perspectives, which may have provided a wealth of knowledge that is now overlooked due to the differing methods.
Then again, we can go back to the first once more. Without short lived generations, true progress can never occur either. Think of the quote that "it takes 20 years for a liberal's ideas to be considered conservative thinking". A generation being roughly 20 years, each new generation tends to imply new ideals, and understanding. 20 years from now gay rights will probably be an assumed concept and those who were against it will seem as quaint and foolish as those who barred black's rights, women's rights, and so on. Only by removing the previous generation from the picture, and placing a new one which had to learn through it, will we progress fully.
If we *DID* suddenly, and magically, create immortality... consider the ramifications it would have socially. We would cease our progress as a whole. Liberal thought would be flattened, and conservative views would hold too much sway... currently we're at a healthy medium; liberal thought creates new ideas, but is tempered by conservative mindset to prevent waste and limit offshoots into worthless endeavours. To heavily overbalance one side or the other is to invite disaster, as both must be maintained.
So although I don't think we're too far off from developing a form of immortality, I do however believe that we are NOT ready for it just yet. The social structuring which would be required to impliment it properly, without destroying us as a whole, is dangerous, as it's going to cause riots no matter whot yeu do. It could be the single worst thing to happen to civilization as a whole if improperly handled, and considering most people won't know how to handle it, and the ones least capable of handling it will be the ones most likely to be in charge of such... well... we'll see how things go, but I can't see it going over too well sadly.