I found the comment honest and thoughtful. I think they are saying, at your ability, the marathon is a risky effort, and if you were really concerned about longevity, you might wait a while to improve and tackle the marathon when you are better prepared. But where you are at, you may need to make compromises such as not running up to the 20 miles. I also agree that you should strongly consider heeding the advice to cap runs at 3 hrs ish because longer doesn’t give you nearly enough benefit compared to risk. If you want further evidence, take it to the extreme and look at ultra runners, say people targeting 100 milers. They are certainly not cranking out 90 mile runs before the race. It may seem daunting to have to cover so much more distance on race day than you’ve done, but I think that strategy works for a lot of people esp from the injury perspective.