They don’t have to be gone. Off the top of my head (Clanand)Post grad I wasn’t really expecting anymore appearances from anyone besides Nagisa but there’s the New Years Party, Kyou as Ushio’s teacher and Fuko waking up. and Little Busters After Riki/Rin runaway and everything is reverted to before they met Kyousuke the rest of the heroine still appear once they’re back in the real world. I’m not expecting them to do anything important though.
My point was more he couldn’t go past 5 years ago (random number means nothing) as in he’d be stopped and the power wouldn’t take him further. How you thought I meant it still works. His weakness is probably needing light though.
Edit: I thought this was in a different thread so forgot about it but just a question for @Pepe about the alt timelines theory (which I do agree with) Wouldn’t Nao and her brother have been caught? Unless creating this alt timeline somehow they were caught instead of Ayumi and Yuu (which I guess would get Shun wanting to help them as it was his fault they were captured).