Is it really necessary to send humans to those places just to get the knock-on benefits? Couldn’t we do those things directly, without going there?
It seems to me that, today, those who have the money to spend on these endeavors would only do so if there were perceived short-term benefits to themselves. That means they plan to exploit the resources, or increase their own power somehow.
I know the good engineers that make this happen are doing it for the challenge and in the pursuit of knowledge, and I know that’s why we poors support it, but that doesn’t “pay the bills.” What is the motivation behind the money? Why are they really doing this?
The problem is that your return to Earth would slowly move you back down the dilation losing the gains.
You can take two routes to a restaurant. One is very short but curvy and has a slow speed limit. The other is a really long straight shot with high speed. You can think of your scenario as such a case where even though the straight path is longer, it takes the same “time” to get to the restaurant.
You would be taking the faster, longer route while Earth takes the windy slow route but as you arrived back you would still be in sync.
Edit to add: Spacetime is a single thing which is why the above behavior the case.
That’s not how time dilation works. Astronauts that have spent significant time on the ISS have experienced — however marginally — less time than their identical twins on Earth.