How Far in Advance Should You Book a Tour
Quick answer: A practical rule of thumb by experience type, not a single blanket number.
How far ahead to book depends heavily on the type of experience, not a single universal rule.
Book weeks ahead
Small-capacity experiences (small boats, limited museum slots, popular day trips in peak season) are worth booking 2-4+ weeks out.
A few days is usually fine
Larger-capacity city tours and standard museum tickets outside peak season rarely require more than a few days' notice.
Same-day can work
For flexible travelers, checking the "last-minute deals" section once you're already at the destination sometimes turns up discounted, still-available slots.
The exception: major holidays
Around major local or international holidays, book earlier than you think you need to, regardless of experience type.