Is it ever better to wait for a last-minute deal?

Rarely. Last-minute 'deal' fares are a relic of the past; airlines now use dynamic pricing that increases costs as the plane fills up, making last-minute bookings the most expensive option.

Does incognito mode actually find cheaper flights?

No. Airlines do not track your search history to hike prices for you specifically. Using incognito mode is fine to keep your browser clean, but it will not lower the fare.

What if the price drops after I book?

If you booked a basic economy ticket, you are likely stuck with it. If you booked a Main Cabin or higher fare, check the airline's policy on 'flight credits'—you may be able to cancel and rebook at the lower rate, receiving the difference as a credit for future travel.

When to book international flights for the best prices

For international travel, the sweet spot for booking is between 3 to 6 months before your departure date. Booking earlier than 6 months usually results in paying a premium, while booking within 3 weeks of departure almost guarantees higher prices.

Set up price alerts early. Six months before your intended travel date, set up price trackers on Google Flights and Skyscanner for your specific route. Do this before you are ready to book so you can learn what the 'normal' price for your route looks like.
Wait for the 'Goldilocks Window'. Monitor your tracked flights. Once you see the price dip below the historical average for that route, book it immediately. For long-haul international flights, this typically happens 90 to 180 days out.
Ignore the 'Tuesday Myth'. Research shows that booking on a specific day of the week, like Tuesday at midnight, does not yield consistent savings. Prices fluctuate based on dynamic demand algorithms, not the day of the week.
Use the 24-hour rule. If you are booking directly through a US-based airline, federal regulations require them to give you a full refund if you cancel within 24 hours of booking, provided the flight is at least 7 days away. Use this to lock in a 'good enough' price while you confirm travel logistics.

Is it ever better to wait for a last-minute deal?: Rarely. Last-minute 'deal' fares are a relic of the past; airlines now use dynamic pricing that increases costs as the plane fills up, making last-minute bookings the most expensive option.
Does incognito mode actually find cheaper flights?: No. Airlines do not track your search history to hike prices for you specifically. Using incognito mode is fine to keep your browser clean, but it will not lower the fare.
What if the price drops after I book?: If you booked a basic economy ticket, you are likely stuck with it. If you booked a Main Cabin or higher fare, check the airline's policy on 'flight credits'—you may be able to cancel and rebook at the lower rate, receiving the difference as a credit for future travel.