Specifically, how long do I need to survive to get enough xp to unlock all the characters, and any other XP based unlocks?

I've got a camp set up such that I can basically go as long as I care to before I off myself to try one of the other characters. I'm only on my second "life" though, so I don't have any idea what the XP scale is.

Is 35 days enough to unlock everything, or do I need to keep merrily farming my way into the future, before stepping off the abyss and starting it all up again with someone new?