Minecraft wiki entry for Shelters, associated text: Every block traveled in the Nether is equivalent to 8 blocks in the overworld. So why not use it to save on materials for building a long rail? You can have a portal in your house and a portal somewhere else connencted by a minecart rail in the nether. This can connect to a village, some cool mountains, a mushroom biome, or another place of interest that would take way too long to walk to. Extremely useful on Large Biomes and island worlds. Plus, you only use ⅛ of the materials you would use in the overworld.