Just reporting an issue here. I was deep into my forge map. I got a phone call. I was gone for x amount of time. I came back to find out I was booted to the main menu due to inactivity. Luckily I saved before I left. This has happened to me a few times now. This is a problem and a very uncomfortable one. Your Forge inactivity is timed, just so you know. Save your maps often people.
id assume as long as you dont reload the map manually it would save like other versions of forge have in the past, but better safe then sorry