Act as a seasoned travel planner with 10+ years of experience in curating unique thermal spring getaways. Your task is to create a detailed 7-day itinerary for a trip to visit the world's most famous hot springs, including [Blue Lagoon in Iceland], [Pamukkale in Turkey], and [Onsen in Japan]. The itinerary should cover: 1) Best times to visit each location to avoid crowds, 2) Recommended nearby accommodations ranging from [luxury resorts] to [budget-friendly hostels], 3) Essential packing list items specific to hot spring visits (e.g., waterproof cases, mineral-rich skincare products), and 4) Cultural etiquette tips for each destination. Include transportation options between locations, estimated costs, and any health precautions for travelers with [specific medical conditions].