realistically grace does not want to live forever. grace barely wants to thinks he deserves to live past next tuesday (we don't have time to get into all that again.) twitch, however, does. in a sense, anyway,, maybe not forever forever. but they want to live for as long as they want. and once they learn they didn't exist before leaving the cage gardens 5 years ago, they only want it more.
it's not fair, that they came into existence in a body already decades old, that they didn't get their younger years to fuck around and discover who they are, that they didn't get a childhood, that they missed out on so much. it's not fair that they only exist from other people's stolen years. it's not fair that they'll only get to spend a couple decades with the people they meet before they're all too old. they didn't even get the chance for longer.
but they want to make that chance, and they don't want to do it alone. they try to pull grace in with them. he's not exactly receptive to it. he's tired. sometimes things aren't fair, and sometimes you just have to make the best of the time you have. (twitch would argue he's not even doing that, though.) twitch says yes, but what if you don't even get the time to make the best of it, if it was never an option for you? what if they want the chance to have a life with him? this, really, is all they've ever known. they want him to heal. they want both of them to find a life away from the tragedies that define them. twitch wants them both to have a chance to live
they meet in the middle. it's reluctant, but yes, grace will live for them, but when he's had enough, they have to promise they'll let him go. twitch agrees. partly because they can't foresee it happening, but also because a part of them knows that when he goes, they'll go with him. they only set out to live for as long as they want, and they don't want more time than grace has.