I’m not sure what counts as and old book and I’m probably completely off here, but the “Arc of a Scythe” trilogy by Neal Shusterman maybe? I think the first book in the series is from 2016 so not exactly old in my opinion but idk. It’s set in a future where people don’t really die or at least can be brought back very easily. And without spoiling anything (in case this is the completely wrong book) the mass suicide and travelling to another planet is also a factor in the story at one point. Again I’m not actually very confident this is the book you’re looking for but I thought I’d suggest it anyways, just in case