There are many reason for it to end eventually. Lol the sun has limited fuel. When it goes out we are all doomed. A Gigantic asteroid will eventually hit earth. It may be millions of years but it will eventually happen. There is also the apocalypse. That will probably include every possible bad thing that could happen put together. All that matters is everyone now will be dead before it happens. Only paranoid people will worry about it right now.
1.sun supernova either freeze or burn
2.andromeda joins us
3.big ass asteroid
5.big random explosion
6.somehow humans eventually have a huge influence on the earth and we all die
9.black hole eventually gets us or we make a black hole
10.aliens? Idk why they would want to destroy us they would just want to know about us