Unless of course someone finds a way to circumvent the mists. If they’re magical in nature, for example, the Blot could negate them with his repaired gauntlet. Or there could be a magical artifact that can allow passage, or Heron or Gandra could whip something up. It’s entirely possible Scrooge could have had Gyro or someone provide easy access before now, but he’s been more than happy with only being able to visit every five years.