Originally Posted by
LizzyDragon84
This is the answer that I was thinking of as well. In the US, the seatbelt sign goes off either at 10,000 or 18,000 ft. (might vary by airline). By that point, the cabin should be at the pressure that it'll stay at until descent.
The seatbelt sign rarely goes off at 10,000' or 18,000'. It goes off when the Captain decides that the flight will be reasonably smooth which could be at just about any altitude though many Captains always wait until reaching cruise altitude.
The pressurization should normally have stopped climbing within 20 minutes of takeoff and will start descending the cabin as soon as the airplane's descent starts.