How far ahead should I book flights and hotels for a Japan ski trip?

Work backwards from what's actually scarce, not from a fixed countdown. Rooms at good hotels near popular resorts are the real bottleneck; plenty of properties open their calendars the better part of a year or more before the season starts, and Japanese and other Asian travellers are already filling them by then.

So hotels come first, before flights are even locked in. Hold something, anything, with a free-cancellation policy the moment you have a rough window in mind, then keep checking back and trading up as better options appear. Wait until you're inside six months of travel and you're picking from what nobody else wanted, at whatever price is left.

International flights are simpler: prices generally drift upward the closer you get to departure, so book as soon as your dates are firm rather than waiting. Domestic connections work in reverse: the budget carriers serving routes like Tokyo to Sapporo typically don't open their flights for booking until a few months before, so trying to lock those down early may mean overpaying for your flights.

Lessons and guides also need to be booked early. As soon as everything else is in place, get onto it. The best English-speaking instructors and guiding outfits often fill their peak-season slots before most travellers have even finished picking a resort, so treat that booking as urgent once your hotel and flights are settled.