Now scientists have discovered many kinds of earth, but what if I don't see immigrants in my lifetime? The earth will die sooner or later, and I can't see aliens.

That's for sure, it can be tens of thousands of light years! If aliens are smart enough to distort space through Einstein's general relativity and use dark matter to cross wormholes, they will come faster. But whether the earth will be finished or not, we will never know, because from the space and probability wave of quantum mechanics, wormhole crossing is considered to be superluminal from a certain point of view. So it's a pity not to see aliens.