Just before my first kill screen I had a 783,600 game.
The funny thing is, since then, I've never had any game end in the 700s. Just that one.
If I go deep, it either ends somewhere in the 600s or I finish (850-890).
Which is nice, knowing that this is the rule, because now when I break 700K I just breathe a sigh of relief knowing that nothing can stop me.
Of course, that only applies to one-hammer runs and I'm not planning to do many of those anymore...