I have some philosophical objections to your approach. I'm not sure it's such a good idea to focus exclusively on research questions that are explicitly aging-related, just because you'll be limiting yourself to a subset of the promising ideas out there. Secondly, you probably shouldn't worry about pursuing a project in which your already-collected data is useless, especially if that data or similar is also available to most other researchers in your field (if not, it would be very useful for you to try to make that data available to others who could do something with it). You're probably more likely to make progress with interesting new data than interesting old data. Also, I'm not sure if this is your intention, but it seems to me that the goal of spending 20 years to slow or prevent aging is a recipe for wasting time. It's such an ambitious goal that so many people are already working on, any one researcher is unlikely to put a measurable dent in it. It's like getting a math phd and saying "Ok, now I'm going to spend the rest of my life trying to help solve the Riemann Hypothesis." Esepcially when you're just starting out, you may be better-served working on the most promising projects you can find in your general area of interest, even if their goals are less ambitious.
P.s. Sorry if a lot of what I've said is naive, I've never worked in academia.
I wasn't arguing whether aging research should receive more attention, just that it receives enough to make a single researcher a drop in the bucket, but you might not be an average researcher. I'm interested in knowing, how likely do you think it is that the life expectancy of some people will be measurably lower if you work as a used-car salesman for the next 20 years rather than a researcher. I'm not suggesting that aging isn't a worthwhile area of research, just that it may be counterproductive for you to be trying to make all the work you do for the next 20 years have some direct bearing on aging.
When I say a project is ambitious, I mean that it is very unlikely to return good results, but that the impact of those good results would be enormous. Developing a large number of drugs to increase the life expectancies of terminally ill cancer patients is less ambitious than trying to cure their cancer. You seem to be thinking that we have made so little progress on aging because it hasn't received enough attention. What if it's the other way around, and so few researchers tackle aging head-on because it's hard to make meaningful progress on? I think that for any researcher who wants to provide mechanistic insights into aging, or figure out how the brain works, or create a machine with human-like general intelligence, there's a lrage incentive for success, but almost inevitably such researchers need shorter term results to keep themselves going. If there simply aren't any shorter term opportunities to make meaningful progress on, they run the risk of working on something that seems related to the problem they set out to solve, but in reality contributes only shallowly to their understanding of it. This is how you end up with so many attempts to better understand the brain through brain scans or make progress in machine intelligence by studying an absurdly specific situation. There were probably more meaningful things those researchers could have been doing that didn't seem to fall under the heading of an extremely ambitious goal. You might be able to bypass these tendencies, but it won't be easy; if it were easy, we would have more researchers who are making meaningful progress on aging.