When should I save to avoid having to replay the whole game?

I'm playing completely blind on my first run. I just assembled the door and I've slept at a campfire with rasta beast. I've only been using one save slot up until now, but are there any points in the game where I should absolutely keep a separate save file to return to later?

I don't want to replay the entire game just for one new ending haha. If you can keep your advice spoiler free ("Save when you see a tree with a blue trunk" type stuff), that'd be great. Thanks!