I don't think it's the fall that matters. The problem would come when the airplane begins to tumble. Rip the tail off a B-52, and I would expect it to rapidly tumble and subsequently disintegrate with unpleasant consequences for those inside. Furthermore, ejecting is probably more likely to succeed in straight and level flight than from a tumbling aircraft. For both reasons, it is desirable to eject quickly once it becomes necessary.
Additionally, a 10 second wait is unnecessary. We see from fighter ejector seats that ejection can be done in just a few seconds. What can possibly be gained by remaining once the seat is ready to eject?
It's a story about a b52 that lost its vertical stabilizer. It flew to the nearest base and landed normally, six hours later at a different base because of wind problems at the first base.
To my anonymous downmodder: the parent's text seemed to think it impressive that B-52s fly at a height where "even a 10-second straight vertical fall should not be a problem".
Basic physics shows that such a height is scarcely more than about 500m, the distance an object in freefall would fall in that time and whatever other distance would be traveled during deceleration.
What, exactly, is the justification for downmodding a comment pointing that out?
