Don't get too much emotional because what you see is might different 10-15 years from now.
Good point, there's also chances that what we are expecting to happened might not favor us, future always have surprises.
Think about how volatile we are and you can't assure that particular project will give you something big profit in the future if you will hold.
But also review and assess what happened 10 years ago, if the market continue being progressive the chance still high to gain good compensations.
As have you said that you are willing to hold for 15 years and the question is if that project will still exist?
Then the process of doing your research and analyze the project is very important, holding long term assets needs strong foundations.
If that you wanted to hold that long and can afford to do that, much better to choose Bitcoin or Ethereum, or BNB, not new projects that have not been proven and tested yet.
Top 3 crypto that already have big supports from, investors, developers and traders. Huge chance to succeed.