An important point made in longevity research like SENS (cf., http://www.sens.org/ http://www.sens.org/ ) is that it should also improve youthful characteristic

An important point made in longevity research like SENS (cf., http://www.sens.org/ http://www.sens.org/ ) is that it should also improve youthful characteristics. This is important, because we shouldn't want to live into our 200's and be as though we're in our 80's (feeble, weak, etc.). True longevity means longevity of youthful biology, including all the attendant benefits that come with youth. In other words, we should seek to reach a point where we reach full maturity (mid 20's or so given some variation) but do not begin deteriorating.