2 Things. 1, I'm not hansel, I'm a mixed build, but If you want to convert, it'd probably be when your next land costs less than a fully upgrade Sub Factory. Also, there's already a thread by Dilly. It's stickied, shouldn't be too hard to miss. 2, Bump Up My Post!
Still not seeing any Mixed guides... i'll keep bumping it, request some additions and I'll try and edit them in