Edward,
The time delay of the air dump can be modified by the folks at Beaver Coach Sales Service Dept. They changed mine to 90 seconds, which dumps all the air. As I recall it was a software download to the control module. I would guess not many shops have access to the software.
Each jack is extended until it hits the frame and jiggles the coach. That jiggle stops the jack. When all 4 are touching the frame, leveling begins. So you have 4 jiggles before leveling starts. The 2 jacks at a time are extended to complete the leveling process. If only one jack were extended, the frame would be twisted. If the left front and right rear were extended together a twist would occur. So only the pairs on the front, rear, or each side will be extended at one time. This will, hopefully, avoid popped windshields. The best way I have found to avoid the earthquake is to leave the coach until it is over.
Full air up before retracting the jacks seems to reduce the rapid free fall when you push the retract button.
Larry