Doesn't matter. Their desire to stay on a ship with no hope or expansion and a place they've admitted they can't sterilize with their tech is a form of madness. Like it or not, they are getting off that ship. Forcing their kids to live their lives in a ship, never basking in a warm day on a real planet, never going where they want with ease, is utter madness. Plus like I said, sell the ship, it's theirs after all, turn it into tourism or a museum piece and give them a ship of equal size these days but with FSD tech/modern medicine/fresh supplies, they can go and drift however long they want and then come back, or head into the void out of the galaxy.
The moment they sent that distress call for help, is the moment they rejoined the populace, and honestly they have lived such sheltered lives they cannot fathom how pointless their little adventure is since the journey that took ages, is now doable in like...5 minutes at most ... with a smallest size E rated FSD....and a tiny fuel tank...
And how less pointless is "adventure" of citizens of Earth, flying in circles around one star?
They traded some comforts of living on a planet for living in a space monastery flying towards unknown. For all intents and purposes this is their "planet". I don't think they care how fast they're going and at least their outside view is always changing.
However, what's going on inside that kind of isolationist colony living on the dying world is interesting subject. I can't quite recall, but I have a feeling there must've been an episode of Star Trek that was about something like that.
It was 'The Orville' had am episode like this, except the occupants didn't know they were on a ship, they didn't know they were heading for a star either.