Here is the original thread about it: biome location
I never figured out the world is infinite thing. I suppose at the north and south poles it would just get so damn cold and barren that the player would not be able to survive for long and have to turn back. Let the cold just keep going, or turn into ocean. Whatever works.
The size of biomes will have to be tested. They need to be somewhat large, especially if vehicles will come. I don't want to be in a new biome every few minutes while driving. It would be great if biomes would take like a in game day or two to cross by foot if you didn't stop (of course you would have to stop no doubt.. so a little longer in the end). I could go larger but I doubt many people want it like that lol