This model assumes that interstellar travel is profitable. There is no evidence that this is the case, even if we had Star Trek technology.
If it isn't profitable, then it turns into a drain on the home planet. That isn't sustainable.
If it isn't profitable, then it turns into a drain on the home planet. That isn't sustainable.
If we want to stay on the profit driven model only then it could still be profitable to send out colonising entities once the solar systems resources are fully utilised. Remote colonies could stream back computational information (say Pixar's Toy Story 42) thus increasing our wealth.
The only way that is going to happen is if a company with profit motive is willing to invest in r and d to bring down the costs.
NASA is incredible, but it isn't moving towards bringing down space exploration costs.
If you only live 100 years and your society will be unrecognizable after 500 years, it's obviously foolish to embark on a project that will turn a profit 1000 years later.
If you can live 1M years and your civilization has been more or less stable for 10M years, you can probably afford to wait 10K years for a shipment of unobtanium. It would be just like a 17th century European merchant who sends a ship to India and waits several months for it to return.
Even if the average lifespan is short, some industries can be profitable across generations. Lumber is often harvested 30-50 years after planting, and I've heard of people investing in coastal redwood that would take 100+ years before they can be cut down.