Booking too far ahead (like months out) often locks you into higher rates before prices settle, and waiting until the last few days usually means slim pickings and whatever's left costs more. The real trap is thinking there's one magic window - it shifts depending on the destination, season, and even the day of the week you're traveling.
For September travel, aiming for 2-3 weeks out is solid, but here's what actually matters: set a price alert on the booking site itself rather than checking manually. Most platforms let you track a specific room and notify you if the price drops. That way you're not guessing when to pull the trigger. Also, check on a Tuesday or Wednesday afternoon - hotels tend to adjust rates mid-week, and you'll often see better pricing than on weekends when people are actively searching.
One thing that usually gets overlooked: call the hotel directly about a week before arrival. Not to negotiate (that rarely works), but staff sometimes know about small discounts or upgrades that don't show online. They can also tell you if a conference or local event is about to tank occupancy, which means prices might shift downward. You've already got your baseline price from browsing, so a quick conversation might land you something better without extra effort.