Question: how long are winds aloft valid for?
Answer: From this table you can see that the 6-hour forecasts are usable from the time they are issued until 3 hours after the valid time. The 12 hour forecasts are usable from -3 to +6 hours of the valid time and 24 hour forecasts are usable from -6 to +6 hours of the valid time. The products are issued 4 times daily.