Even if we lived 120 years in average, do you think the game would change a lot, I don't. I don't see drastic changes in young people today, yet they'll most likely be alive in 60-70 years. And for argument's sake, even if it does we still end up with much more people living on the same resource limited planet at the same time.
You can already bump your life expectancy (and end life quality) quite a lot by eating health, exercising, quitting drinking/smoking. Most people don't do it because it's too much effort and "that's not life", again individualism/short sightedness.
We need a cure for laziness / individualism, then, maybe, we can start talking considering longevity.
This is exactly the reason these scientists are focusing on genetic and other medical ways to increase lifespan, which are going to be packaged in products that can be used without effort. One might say what they want about people not wanting to expend unnecessary effort, one might call it lazy or just smart, or a drive of progress, it doesn't matter. The fact is if you give people a method that requries less effort, more people will use it. Thus we will have a greater general effect on the population with these methods.
Giving lazy people the opportunity to continue living lazily longer while ravaging the planet ? Welcome to transhumanists paradise I guess.
Then there's also other (more economical, but you could say that's caused by psychology as well) reasons, such as tragedy of the commons.
People fearing flying more than driving are not afraid of the relative chances of dying (which are low either way). They are afraid of the feeling and experience of spending long time in a falling plane knowing that you are going to die, being stuck in one seat and not being able to do anything about it. This does not happen when you are driving, if there is an accident, you usually either die instantly or in some rare cases receive some injuries, but at least then you can lie at the site of the accident and hope that medics will come. It's not the same as being stuck in a box for 10s of minutes knowing you are most likely about to crash to a painful death. You have to spend time in that experience, to feel it, in a completely hopeless state. That's why people afraid of flying, not because of some statistics.
If we manage to extend the expected (or even just possible) generic lifespan of normal people - that will be one of the best promoters of environment-thinking of normal population. Because suddenly the choices they make today become very real in terms of impact on the environment in the next 50-100-200 years, because there is a good change that this same person is going to be living at that time.