This is just my inner space opera lover voice coming out. A huge part of the story I'm thinking about takes place during outbound flights out of our solar system, likely to Epsilon Eridani, because it's close and has planets.
Epsilon Eridani. Is like what? 10 Light years away? And it has planets? So assuming we only are able to make half light speed, round trip we're talking about 40 or 50 years, which would be less in subjective time because of relativistic effects. Ok, so it's still hard. You'd have to send people who were twenty, and they'd get back 40 years later, though though the subjective time is only about 5-10 years. The faster you go, the shorter it seems to take, relative to how long it actually takes.
This is all based on the supposition that extraterrestrial colonization at a certain point, doesn't need to be based upon finding Earth-Like planets, but rather be based on finding places where we can build reasonably self-sustaining domes, or really just landed spaceships. Planets are nice, and they mean that you don't have to expend energy to maintain a course, and that hopefully you have resources that you can mine near by that are accessible. If you build/design the habitats right, it right it'd work fine or at least fine enough for a novel.
That's my story and I'm sticking to it.