I would definitely die to save others - whether in eternal life or for the rest of their life on this planet wouldn't matter. I would not likely sacrifice myself for just one other person... Simply because I believe there is more good I could do with my life that throwing it away for someone else. And the reason why has nothing to do with a belief in the afterlife. One's death is their final act in this world. I would want my final act to be as significant as possible, and sacrificing myself to save others (the more, the better) would be the most significant.